diff --git a/racket/src/racket/src/Makefile.in b/racket/src/racket/src/Makefile.in
index bfe89ee8df..76528c1549 100644
--- a/racket/src/racket/src/Makefile.in
+++ b/racket/src/racket/src/Makefile.in
@@ -422,7 +422,7 @@ setjmpup.@LTO@: $(COMMON_HEADERS) \
          $(srcdir)/stypes.h   $(srcdir)/schmach.h
 sfs.@LTO@: $(COMMON_HEADERS) \
          $(srcdir)/stypes.h $(srcdir)/mzmark_sfs.inc
-string.@LTO@: $(COMMON_HEADERS) \
+string.@LTO@: $(COMMON_HEADERS) $(RKTIO_HEADERS) \
          $(srcdir)/stypes.h    $(srcdir)/schvers.h $(srcdir)/mzmark_string.inc $(srcdir)/strops.inc \
          $(srcdir)/schustr.inc $(srcdir)/systype.inc
 struct.@LTO@: $(COMMON_HEADERS) \
diff --git a/racket/src/racket/src/file.c b/racket/src/racket/src/file.c
index 4ef3785b9b..2f88ea861e 100644
--- a/racket/src/racket/src/file.c
+++ b/racket/src/racket/src/file.c
@@ -1043,9 +1043,7 @@ char *scheme_os_getcwd(char *buf, int buflen, int *actlen, int noexn)
     *actlen = slen+1;
 
   if (buflen < slen) {
-    buf = scheme_strdup(s);
-    free(s);
-    return buf;
+    return scheme_strdup_and_free(s);
   } else {
     memcpy(buf, s, slen+1);
     free(s);
@@ -1720,10 +1718,7 @@ static char *do_expand_filename(Scheme_Object *o, char* filename, int ilen, cons
                          errorin, filename);
       }
 
-      filename = scheme_strdup(new_filename);
-      free(new_filename);
-  
-      filename = new_filename;
+      filename = scheme_strdup_and_free(new_filename);
       ilen = strlen(filename);
     }
 #endif
diff --git a/racket/src/racket/src/salloc.c b/racket/src/racket/src/salloc.c
index ac596cd374..a168c7f111 100644
--- a/racket/src/racket/src/salloc.c
+++ b/racket/src/racket/src/salloc.c
@@ -547,7 +547,7 @@ scheme_calloc (size_t num, size_t size)
   memset(space, 0, (num*size));
 #endif
 
-  return (space);
+  return space;
 }
 
 char *
@@ -558,7 +558,7 @@ scheme_strdup(const char *str)
 
   len = strlen(str) + 1;
   naya = (char *)scheme_malloc_atomic (len * sizeof (char));
-  memcpy (naya, str, len);
+  memcpy(naya, str, len);
 
   return naya;
 }
@@ -571,7 +571,22 @@ scheme_strdup_eternal(const char *str)
 
   len = strlen(str) + 1;
   naya = (char *)scheme_malloc_eternal(len * sizeof (char));
-  memcpy (naya, str, len);
+  memcpy(naya, str, len);
+
+  return naya;
+}
+
+char *
+scheme_strdup_and_free(const char *str)
+{
+  char *naya;
+  intptr_t len;
+
+  len = strlen(str) + 1;
+  naya = (char *)scheme_malloc_atomic (len * sizeof (char));
+  memcpy(naya, str, len);
+
+  free((void *)str);
 
   return naya;
 }
diff --git a/racket/src/racket/src/schpriv.h b/racket/src/racket/src/schpriv.h
index 0c45bda527..2f725c2528 100644
--- a/racket/src/racket/src/schpriv.h
+++ b/racket/src/racket/src/schpriv.h
@@ -4568,6 +4568,7 @@ int scheme_regexp_match_p(Scheme_Object *regexp, Scheme_Object *target);
 Scheme_Object *scheme_gensym(Scheme_Object *base);
 Scheme_Object *scheme_symbol_to_string(Scheme_Object *sym);
 
+char *scheme_strdup_and_free(const char *str);
 
 Scheme_Object *scheme_maybe_build_path(Scheme_Object *base, Scheme_Object *elem);
 
diff --git a/racket/src/racket/src/string.c b/racket/src/racket/src/string.c
index a342241849..c64fab04ac 100644
--- a/racket/src/racket/src/string.c
+++ b/racket/src/racket/src/string.c
@@ -25,6 +25,7 @@
 
 #include "schpriv.h"
 #include "schvers.h"
+#include "schrktio.h"
 #include <string.h>
 #include <ctype.h>
 #ifdef NO_ERRNO_GLOBAL
@@ -384,8 +385,6 @@ ROSYM static Scheme_Object *platform_3m_path, *platform_cgc_path;
 READ_ONLY static Scheme_Object *zero_length_char_string;
 READ_ONLY static Scheme_Object *zero_length_byte_string;
 
-SHARED_OK static Scheme_Hash_Table *putenv_str_table;
-
 SHARED_OK static char *embedding_banner;
 SHARED_OK static Scheme_Object *vers_str;
 SHARED_OK static Scheme_Object *banner_str;
@@ -469,8 +468,6 @@ scheme_init_string (Scheme_Env *env)
   platform_cgc_path = scheme_make_path(SCHEME_PLATFORM_LIBRARY_SUBPATH SPLS_SUFFIX);
   platform_3m_path = scheme_make_path(SCHEME_PLATFORM_LIBRARY_SUBPATH SPLS_SUFFIX MZ3M_SUBDIR);
 
-  REGISTER_SO(putenv_str_table);
-
   REGISTER_SO(embedding_banner);
   REGISTER_SO(vers_str);
   REGISTER_SO(banner_str);
@@ -2211,16 +2208,6 @@ int scheme_any_string_has_null(Scheme_Object *o)
 /* Environment Variables                                               */
 /***********************************************************************/
 
-#if defined(OS_X) && !TARGET_OS_IPHONE
-# include <crt_externs.h>
-# define GET_ENVIRON_ARRAY *_NSGetEnviron()
-#endif
-
-#if !defined(DOS_FILE_SYSTEM) && !defined(GET_ENVIRON_ARRAY)
-extern char **environ;
-# define GET_ENVIRON_ARRAY environ
-#endif
-
 #define SCHEME_ENVVARS_TABLE(ev) ((Scheme_Hash_Tree *)SCHEME_PTR_VAL(ev))
 
 Scheme_Object *scheme_make_environment_variables(Scheme_Hash_Tree *ht)
@@ -2253,138 +2240,56 @@ static Scheme_Object *current_environment_variables(int argc, Scheme_Object *arg
   return v;
 }
 
-#if defined(MZ_USE_PLACES) && defined(MZ_PRECISE_GC)
-static char* clone_str_with_gc(const char* buffer) {
-  int length;
-  char *newbuffer;
-  length = strlen(buffer);
-  newbuffer = scheme_malloc_atomic(length+1);
-  memcpy(newbuffer, buffer, length+1);
-  return newbuffer;
-}
-#endif
-
-static void create_putenv_str_table_if_needed() {
-  if (!putenv_str_table) {
-    putenv_str_table = scheme_make_hash_table(SCHEME_hash_string);
-  }
-}
-
-#ifndef DOS_FILE_SYSTEM
-static void putenv_str_table_put_name(const char *name, char *value) {
-#if defined(MZ_USE_PLACES) && defined(MZ_PRECISE_GC)
-  void *original_gc;
-  const char *name_copy;
-  original_gc = GC_switch_to_master_gc();
-  scheme_start_atomic();
-
-  name_copy = clone_str_with_gc(name);
-  create_putenv_str_table_if_needed();
-  scheme_hash_set(putenv_str_table, (Scheme_Object *)name_copy, (Scheme_Object *)value);
-
-  scheme_end_atomic_no_swap();
-  GC_switch_back_from_master(original_gc);
-#else
-  create_putenv_str_table_if_needed();
-  scheme_hash_set(putenv_str_table, (Scheme_Object *)name, (Scheme_Object *)value);
-#endif
-}
-#endif
-
-#if defined(MZ_PRECISE_GC)
-static Scheme_Object *putenv_str_table_get(const char *name) {
-#if defined(MZ_USE_PLACES) && defined(MZ_PRECISE_GC)
-  void *original_gc;
-  Scheme_Object *value; 
-  original_gc = GC_switch_to_master_gc();
-  scheme_start_atomic();
-
-  create_putenv_str_table_if_needed();
-  value = scheme_hash_get(putenv_str_table, (Scheme_Object *)name);
-
-  scheme_end_atomic_no_swap();
-  GC_switch_back_from_master(original_gc);
-  return value;
-#else
-  create_putenv_str_table_if_needed();
-  return scheme_hash_get(putenv_str_table, (Scheme_Object *)name);
-#endif
-}
-#endif
-
-
 static int sch_bool_getenv(const char* name);
 
-void
-scheme_init_getenv(void)
+void scheme_init_getenv(void)
 {
   if (sch_bool_getenv("PLTNOMZJIT")) {
       scheme_set_startup_use_jit(0);
   }
 }
 
-#ifdef DOS_FILE_SYSTEM
-# include <windows.h>
-static char *dos_win_getenv(const char *name) {
-  int value_size;
-  value_size = GetEnvironmentVariableW(WIDE_PATH(name), NULL, 0);
-  if (value_size) {
-    wchar_t *value;
-    int got;
-    value = scheme_malloc_atomic(sizeof(wchar_t) * value_size);
-    got = GetEnvironmentVariableW(WIDE_PATH(name), value, value_size);
-    if (got < value_size)
-      value[got] = 0;
-    return NARROW_PATH(value);
-  }
-  return NULL;
-}
-#endif
-
 static int sch_bool_getenv(const char* name)
 {
-  int rc = 0;
-
-#ifdef DOS_FILE_SYSTEM
-  if (GetEnvironmentVariable(name, NULL, 0)) rc = 1;
-#else
-  if (getenv(name)) rc = 1;
-#endif
-
-  return rc;
+  if (rktio_getenv(scheme_rktio, name))
+    return 1;
+  else
+    return 0;
 }
 
 int byte_string_ok_name(Scheme_Object *o)
 {
   const char *s = SCHEME_BYTE_STR_VAL(o);
   int i = SCHEME_BYTE_STRTAG_VAL(o);
-#ifdef DOS_FILE_SYSTEM
-  if (!i) return 0;
-#endif  
+
   while (i--) {
-    if (!s[i] || s[i] == '=')
+    if (!s[i])
       return 0;
   }
+
+  return rktio_is_ok_envvar_name(scheme_rktio, s);
+    
   return 1;
 }
 
 static Scheme_Object *normalize_env_case(Scheme_Object *bs)
 {
-#ifdef DOS_FILE_SYSTEM
-  bs = scheme_byte_string_to_char_string(bs);
-  bs = string_locale_downcase(1, &bs);
-  bs = scheme_char_string_to_byte_string(bs);
-#endif
+  if (rktio_are_envvar_names_case_insensitive(scheme_rktio)) {
+    bs = scheme_byte_string_to_char_string(bs);
+    bs = string_locale_downcase(1, &bs);
+    bs = scheme_char_string_to_byte_string(bs);
+  }
   return bs;
 }
 
 char *scheme_getenv(char *name)
 {
-#ifdef DOS_FILE_SYSTEM
-  return dos_win_getenv(name);
-#else
-  return getenv(name);
-#endif
+  char *s;
+  s = rktio_getenv(scheme_rktio, name);
+  if (s)
+    return scheme_strdup_and_free(s);
+  else
+    return NULL;
 }
 
 static Scheme_Object *sch_getenv(int argc, Scheme_Object *argv[])
@@ -2408,9 +2313,14 @@ static Scheme_Object *sch_getenv(int argc, Scheme_Object *argv[])
   if (!ht) {
     name = SCHEME_BYTE_STR_VAL(bs);
 
-    value = scheme_getenv(name);
+    value = rktio_getenv(scheme_rktio, name);
+    if (value) {
+      val = scheme_make_byte_string(value);
+      free(value);
+    } else
+    val = scheme_false;
 
-    return value ? scheme_make_byte_string(value) : scheme_false;
+    return val;
   } else {
     bs = normalize_env_case(bs);
     val = scheme_hash_tree_get(ht, bs);
@@ -2418,69 +2328,12 @@ static Scheme_Object *sch_getenv(int argc, Scheme_Object *argv[])
   }
 }
 
-#ifndef DOS_FILE_SYSTEM
-static int sch_unix_putenv(const char *var, const char *val, const intptr_t varlen, const intptr_t vallen) {
-  char *buffer;
-  intptr_t total_length, r;
-  total_length = varlen + vallen + 2;
-
-  if (val) {
-#ifdef MZ_PRECISE_GC
-    /* Can't put movable string into environ array */
-    buffer = malloc(total_length);
-#else
-    buffer = (char *)scheme_malloc_atomic(total_length);
-#endif
-
-    memcpy(buffer, var, varlen);
-    buffer[varlen] = '=';
-    memcpy(buffer + varlen + 1, val, vallen + 1);
-  } else {
-    buffer = NULL;
-  }
-
-  if (buffer)
-    r = putenv(buffer);
-  else {
-    /* on some platforms, unsetenv() returns void */
-    unsetenv(var);
-    r = 0;
-  }
-
-  if (!r) {
-#ifdef MZ_PRECISE_GC
-    char *oldbuffer;
-
-    /* Will free old, if in table: */
-    oldbuffer = (char *)putenv_str_table_get(var);
-#endif
-
-    /* If precise GC, the buffer needs to be remembered so it can be freed;
-       otherwise, the buffer needs to be referenced so it doesn't get GCed */
-    putenv_str_table_put_name(var, buffer);
-
-#ifdef MZ_PRECISE_GC
-    if (oldbuffer)
-      free(oldbuffer);
-#endif
-  } else {
-#ifdef MZ_PRECISE_GC
-    if (buffer)
-      free(buffer);
-#endif
-  }
-
-  return r;
-}
-#endif
-
 static Scheme_Object *sch_putenv(int argc, Scheme_Object *argv[])
 {
   Scheme_Object *varbs, *valbs, *ev;
   Scheme_Hash_Tree *ht;
   char *var;
   char *val;
-  int rc = 0, errid = 0;
 
   if (!SAME_TYPE(SCHEME_TYPE(argv[0]), scheme_environment_variables_type))
     scheme_wrong_contract("environment-variables-set!", "environment-variables?", 0, argc, argv);
@@ -2524,23 +2377,13 @@ static Scheme_Object *sch_putenv(int argc, Scheme_Object *argv[])
       val = SCHEME_BYTE_STR_VAL(valbs);
     }
 
-#ifdef DOS_FILE_SYSTEM
-    rc = !SetEnvironmentVariable(var, val);
-    if (rc)
-      errid = GetLastError();
-#else
-    rc = sch_unix_putenv(var, val, SCHEME_BYTE_STRLEN_VAL(varbs), (val ? SCHEME_BYTE_STRLEN_VAL(valbs) : 0));
-    errid = errno;
-#endif
-
-    if (rc) {
+    if (!rktio_setenv(scheme_rktio, var, val)) {
       if (argc > 3)
         return _scheme_tail_apply(argv[3], 0, NULL);
       else {
         scheme_raise_exn(MZEXN_FAIL,
                          "environment-variables-set!: change failed\n"
-                         "  system error: %e",
-                         errid);
+                         "  system error: %E");
       }
     }
 
@@ -2562,52 +2405,20 @@ static Scheme_Object *env_copy(int argc, Scheme_Object *argv[])
   /* copy system environment variables into a hash table: */
   ht = scheme_make_hash_tree(SCHEME_hashtr_equal);
 
-#ifdef DOS_FILE_SYSTEM
   {
-    char *p;
-    GC_CAN_IGNORE wchar_t *e;
-    int i, start, j;
+    intptr_t i;
+    rktio_envvars_t *envvars;
     Scheme_Object *var, *val;
 
-    e = GetEnvironmentStringsW();
-
-    for (i = 0; e[i]; ) {
-      start = i;
-      while (e[i]) { i++; }
-      p = NARROW_PATH(e XFORM_OK_PLUS start);
-      for (j = 0; p[j] && p[j] != '='; j++) {
-      }
-      if (j && p[j]) {
-        var = scheme_make_immutable_sized_byte_string(p, j, 1);
-        val = scheme_make_immutable_sized_byte_string(p XFORM_OK_PLUS j + 1, -1, 1);
-        var = normalize_env_case(var);
-        ht = scheme_hash_tree_set(ht, var, val);
-      }
-      i++;
+    envvars = rktio_envvars(scheme_rktio);
+    for (i = rktio_envvars_count(scheme_rktio, envvars); i--; ) {
+      var = scheme_make_immutable_sized_byte_string(rktio_envvars_name_ref(scheme_rktio, envvars, i), -1, 1);
+      val = scheme_make_immutable_sized_byte_string(rktio_envvars_value_ref(scheme_rktio, envvars, i), -1, 1);
+      ht = scheme_hash_tree_set(ht, var, val);
     }
 
-    FreeEnvironmentStringsW(e);
+    rktio_envvars_free(scheme_rktio, envvars);
   }
-#else
-  {
-    int i, j;
-    char **ea, *p;
-    Scheme_Object *var, *val;
-
-    ea = GET_ENVIRON_ARRAY;
-
-    for (i = 0; ea[i]; i++) {
-      p = ea[i];
-      for (j = 0; p[j] && p[j] != '='; j++) {
-      }
-      if (p[j]) {
-        var = scheme_make_immutable_sized_byte_string(p, j, 1);
-        val = scheme_make_immutable_sized_byte_string(p XFORM_OK_PLUS j + 1, -1, 1);
-        ht = scheme_hash_tree_set(ht, var, val);
-      }
-    }
-  }
-#endif
 
   return scheme_make_environment_variables(ht);
 }
@@ -2674,99 +2485,52 @@ static Scheme_Object *sch_getenv_names(int argc, Scheme_Object *argv[])
   return r;
 }
 
-#ifdef DOS_FILE_SYSTEM
-static int wc_strlen(const wchar_t *ws)
-{
-  int l;
-  for (l =0; ws[l]; l++) { }
-  return l;
-}
-#endif
+/* Temporarily use internal function: */
+extern void *rktio_envvars_to_block(rktio_t *rktio, rktio_envvars_t *envvars);
 
+/* This will go away when we use rktio processes: */
 void *scheme_environment_variables_to_block(Scheme_Object *ev, int *_need_free)
 {
+  
   Scheme_Hash_Tree *ht;
   Scheme_Object *key, *val;
-  
-  ht = SCHEME_ENVVARS_TABLE(ev);
-  if (!ht) {
-    *_need_free = 0;
-#ifdef DOS_FILE_SYSTEM
-    return NULL;
-#else
-    return GET_ENVIRON_ARRAY;
-#endif
-  }
+  void *p;
 
   *_need_free = 1;
 
-#ifdef DOS_FILE_SYSTEM
-  {
-    mzlonglong i;
-    int len = 0, slen;
-    GC_CAN_IGNORE wchar_t *r, *s;
+  ht = SCHEME_ENVVARS_TABLE(ev);
+  if (!ht) {
+    rktio_envvars_t *envvars;
+    envvars = rktio_envvars(scheme_rktio);
 
-    for (i = scheme_hash_tree_next(ht, -1); i != -1; i = scheme_hash_tree_next(ht, i)) {
-      scheme_hash_tree_index(ht, i, &key, &val);
-      len += wc_strlen(WIDE_PATH(SCHEME_BYTE_STR_VAL(key)));
-      len += wc_strlen(WIDE_PATH(SCHEME_BYTE_STR_VAL(val)));
-      len += 2;
-    }
+    p = rktio_envvars_to_block(scheme_rktio, envvars);
+    
+    rktio_envvars_free(scheme_rktio, envvars);
 
-    r = (wchar_t *)malloc((len + 1) * sizeof(wchar_t));
-
-    len = 0;
-
-    for (i = scheme_hash_tree_next(ht, -1); i != -1; i = scheme_hash_tree_next(ht, i)) {
-      scheme_hash_tree_index(ht, i, &key, &val);
-      s = WIDE_PATH(SCHEME_BYTE_STR_VAL(key));
-      slen = wc_strlen(s);
-      memcpy(r XFORM_OK_PLUS len, s, slen * sizeof(wchar_t));
-      len += slen;
-      r[len++] = '=';
-      s = WIDE_PATH(SCHEME_BYTE_STR_VAL(val));
-      slen = wc_strlen(s);
-      memcpy(r XFORM_OK_PLUS len, s, slen * sizeof(wchar_t));
-      len += slen;
-      r[len++] = 0;
-    }
-    r[len] = 0;
-
-    return r;
+    return p;
   }
-#else
+
   {
-    GC_CAN_IGNORE char **r, *s;
+    rktio_envvars_t *envvars;
     mzlonglong i;
-    intptr_t len = 0, slen, c;
 
+    envvars = rktio_empty_envvars(scheme_rktio);
+    
     for (i = scheme_hash_tree_next(ht, -1); i != -1; i = scheme_hash_tree_next(ht, i)) {
       scheme_hash_tree_index(ht, i, &key, &val);
-      len += SCHEME_BYTE_STRLEN_VAL(key);
-      len += SCHEME_BYTE_STRLEN_VAL(val);
-      len += 2;
+
+      rktio_envvars_set(scheme_rktio,
+                        envvars,
+                        SCHEME_BYTE_STR_VAL(key),
+                        SCHEME_BYTE_STR_VAL(val));
     }
 
-    r = (char **)malloc((ht->count+1) * sizeof(char*) + len);
-    s = (char *)(r + (ht->count+1));
-    c = 0;
-    for (i = scheme_hash_tree_next(ht, -1); i != -1; i = scheme_hash_tree_next(ht, i)) {
-      scheme_hash_tree_index(ht, i, &key, &val);
-      r[c++] = s;
-      slen = SCHEME_BYTE_STRLEN_VAL(key);
-      memcpy(s, SCHEME_BYTE_STR_VAL(key), slen);
-      s[slen] = '=';
-      s = s XFORM_OK_PLUS (slen + 1);
-      slen = SCHEME_BYTE_STRLEN_VAL(val);
-      memcpy(s, SCHEME_BYTE_STR_VAL(val), slen);
-      s[slen] = 0;
-      s = s XFORM_OK_PLUS (slen + 1);
-    }
-    r[c] = NULL;
+    p = rktio_envvars_to_block(scheme_rktio, envvars);
 
-    return r;
+    rktio_envvars_free(scheme_rktio, envvars);
+
+    return p;
   }
-#endif
 }
 
 /***********************************************************************/
diff --git a/racket/src/rktio/rktio.h b/racket/src/rktio/rktio.h
index 5cf6fe984e..24f565bb04 100644
--- a/racket/src/rktio/rktio.h
+++ b/racket/src/rktio/rktio.h
@@ -169,19 +169,39 @@ RKTIO_EXTERN int rktio_udp_change_multicast_group(rktio_t *rktio, rktio_fd_t *rf
 /*************************************************/
 /* Environment variables                         */
 
+/* Check whether a string is valid as a new (e.g., no "=") */
+RKTIO_EXTERN int rktio_is_ok_envvar_name(rktio_t *rktio, const char *name);
+
+/* Checks whether environment variables are case-folded by the OS.
+   That doesn't mean that clients need to case-fold names, but clients
+   may want to immitate the OS. */
+RKTIO_EXTERN int rktio_are_envvar_names_case_insensitive(rktio_t *rktio);
+
+/* Gets an environment variable value, or reports
+   `RKTIO_ERROR_NO_SUCH_ENVVAR` when returning NULL; the result must
+   be freed. */
+RKTIO_EXTERN char *rktio_getenv(rktio_t *rktio, const char *name);
+
+/* Set an environment variable's value, where a NULL value for `val`
+   unsets it. */
+RKTIO_EXTERN rktio_ok_t rktio_setenv(rktio_t *rktio, const char *name, const char *val);
+
 typedef struct rktio_envvars_t rktio_envvars_t;
 
-RKTIO_EXTERN char *rktio_getenv(rktio_t *rktio, char *name);
-RKTIO_EXTERN int rktio_setenv(rktio_t *rktio, const char *name, const char *val);
-
+/* Extracts all environment variables into a record */
 RKTIO_EXTERN rktio_envvars_t *rktio_envvars(rktio_t *rktio);
+/* Create an empty environment-variables record: */
 RKTIO_EXTERN rktio_envvars_t *rktio_empty_envvars(rktio_t *rktio);
+/* Clones an environment-variable record: */
 RKTIO_EXTERN rktio_envvars_t *rktio_envvars_copy(rktio_t *rktio, rktio_envvars_t *envvars);
+/* Deallocates an environment-variables record: */
 RKTIO_EXTERN void rktio_envvars_free(rktio_t *rktio, rktio_envvars_t *envvars);
 
+/* Access/update environment-variables record by name: */
 RKTIO_EXTERN char *rktio_envvars_get(rktio_t *rktio, rktio_envvars_t *envvars, char *name);
 RKTIO_EXTERN void rktio_envvars_set(rktio_t *rktio, rktio_envvars_t *envvars, char *name, char *value);
 
+/* Access/update environment-variables record by index: */
 RKTIO_EXTERN intptr_t rktio_envvars_count(rktio_t *rktio, rktio_envvars_t *envvars);
 RKTIO_EXTERN char *rktio_envvars_name_ref(rktio_t *rktio, rktio_envvars_t *envvars, intptr_t i);
 RKTIO_EXTERN char *rktio_envvars_value_ref(rktio_t *rktio, rktio_envvars_t *envvars, intptr_t i);
@@ -496,6 +516,7 @@ enum {
   RKTIO_ERROR_TRY_AGAIN, /* for UDP */
   RKTIO_ERROR_TRY_AGAIN_WITH_IPV4, /* for TCP listen */
   RKTIO_ERROR_TIME_OUT_OF_RANGE,
+  RKTIO_ERROR_NO_SUCH_ENVVAR,
 };
 
 /* GAI error sub-codes */
diff --git a/racket/src/rktio/rktio_envvars.c b/racket/src/rktio/rktio_envvars.c
index 748c0829d3..2ddd0cd3b8 100644
--- a/racket/src/rktio/rktio_envvars.c
+++ b/racket/src/rktio/rktio_envvars.c
@@ -19,15 +19,40 @@ extern char **environ;
 # define GET_ENVIRON_ARRAY environ
 #endif
 
-char *rktio_getenv(rktio_t *rktio, char *name)
+
+int rktio_is_ok_envvar_name(rktio_t *rktio, const char *s)
+{
+  int i = strlen(s);
+#ifdef RKTIO_SYSTEM_WINDOWS
+  if (!s[0]) return 0;
+#endif  
+  while (i--) {
+    if (s[i] == '=')
+      return 0;
+  }
+  return 1;
+}
+
+int rktio_are_envvar_names_case_insensitive(rktio_t *rktio)
+{
+#ifdef RKTIO_SYSTEM_WINDOWS
+  return 1;
+#else
+  return 0;
+#endif
+}
+
+char *rktio_getenv(rktio_t *rktio, const char *name)
 {
 #ifdef RKTIO_SYSTEM_UNIX
   char *s;
   s = getenv(name);
   if (s)
     return MSC_IZE(strdup)(s);
-  else
+  else {
+    set_racket_error(RKTIO_ERROR_NO_SUCH_ENVVAR);
     return NULL;
+  }
 #endif
 #ifdef RKTIO_SYSTEM_WINDOWS
   intptr_t value_size;
@@ -44,6 +69,7 @@ char *rktio_getenv(rktio_t *rktio, char *name)
     free(value_w);
     return value;
   }
+  set_racket_error(RKTIO_ERROR_NO_SUCH_ENVVAR);
   return NULL;
 #endif
 }
@@ -52,25 +78,13 @@ int rktio_setenv(rktio_t *rktio, const char *name, const char *val)
 {
 #ifdef RKTIO_SYSTEM_UNIX
   if (val) {
-    char *buffer;
-    intptr_t total_length, r, varlen, vallen;
-    
-    varlen = strlen(name);
-    vallen = strlen(val);
-    total_length = varlen + vallen + 2;
-    
-    buffer = malloc(total_length);
-    
-    memcpy(buffer, name, varlen);
-    buffer[varlen] = '=';
-    memcpy(buffer + varlen + 1, val, vallen + 1);
+    int r;
 
-    r = putenv(buffer);
+    r = setenv(name, val, 1);
+    
     if (r)
       get_posix_error();
 
-    free(buffer);
-
     return (r ? 0 : 1);
   } else {
     /* on some platforms, unsetenv() returns void */
@@ -238,6 +252,7 @@ static void envvars_resize(rktio_envvars_t *envvars, intptr_t new_size)
   free(envvars->names);
   free(envvars->vals);
   
+  envvars->size = new_size;
   envvars->names = new_names;
   envvars->vals = new_vals;
 }
diff --git a/racket/src/rktio/rktio_error.c b/racket/src/rktio/rktio_error.c
index 0560bbd954..8a061205b8 100644
--- a/racket/src/rktio/rktio_error.c
+++ b/racket/src/rktio/rktio_error.c
@@ -32,6 +32,7 @@ err_str_t err_strs[]  = {
   { RKTIO_ERROR_TRY_AGAIN, "no UDP message available" },
   { RKTIO_ERROR_TRY_AGAIN_WITH_IPV4, "listen failed, but try again with just IPv4 addresses" },
   { RKTIO_ERROR_TIME_OUT_OF_RANGE, "time value out-of-range for date conversion" },
+  { RKTIO_ERROR_NO_SUCH_ENVVAR, "no value as an environment variable" },
   { 0, NULL }
 };