diff --git a/src/mzscheme/src/file.c b/src/mzscheme/src/file.c
index ff5bf70cd2..8b7c7cbb8c 100644
--- a/src/mzscheme/src/file.c
+++ b/src/mzscheme/src/file.c
@@ -5384,10 +5384,10 @@ static Scheme_Object *file_size(int argc, Scheme_Object *argv[])
  }
 #else
   {
-    struct MSC_IZE(BIG_OFF_T_IZE(stat)) buf;
+    struct BIG_OFF_T_IZE(stat) buf;
 
     while (1) {
-      if (!MSC_W_IZE(BIG_OFF_T_IZE(stat))(MSC_WIDE_PATH(filename), &buf))
+      if (!BIG_OFF_T_IZE(stat)(MSC_WIDE_PATH(filename), &buf))
 	break;
       else if (errno != EINTR)
 	goto failed;
diff --git a/src/mzscheme/src/fun.c b/src/mzscheme/src/fun.c
index 3bf5eeff65..a010b00851 100644
--- a/src/mzscheme/src/fun.c
+++ b/src/mzscheme/src/fun.c
@@ -7340,7 +7340,7 @@ long scheme_get_milliseconds(void)
 # ifdef USE_FTIME
   struct MSC_IZE(timeb) now;
   MSC_IZE(ftime)(&now);
-  return now.time * 1000 + now.millitm;
+  return (long)(now.time * 1000 + now.millitm);
 # else
 #  ifdef PALMOS_STUFF
   /* FIXME */
@@ -7439,7 +7439,7 @@ long scheme_get_seconds(void)
 #  ifdef USE_FTIME
   struct MSC_IZE(timeb) now;
   MSC_IZE(ftime)(&now);
-  return now.time;
+  return (long)now.time;
 #  else
 #   ifdef USE_PLAIN_TIME
   time_t now;
diff --git a/src/mzscheme/src/port.c b/src/mzscheme/src/port.c
index fda273fc4e..b3fc312e3c 100644
--- a/src/mzscheme/src/port.c
+++ b/src/mzscheme/src/port.c
@@ -241,6 +241,11 @@ typedef struct Scheme_FD {
 # define FILENAME_EXN_E "%e"
 #endif
 
+#if defined(DOS_FILE_SYSTEM)
+# define fseeko _fseeki64
+# define ftello _ftelli64
+#endif
+
 /******************** Globals and Prototypes ********************/
 
 /* globals */
@@ -4160,10 +4165,17 @@ scheme_file_position(int argc, Scheme_Object *argv[])
       
 # ifdef WINDOWS_FILE_HANDLES
       {
-        
-        if (!SetFilePointerEx((HANDLE)fd, nll, NULL, 
-                              ((whence == SEEK_SET) ? FILE_BEGIN : FILE_END)))
+	DWORD r;
+	LONG lo_w, hi_w;
+	lo_w = (LONG)(nll & 0xFFFFFFFF);
+	hi_w = (LONG)(nll >> 32);
+        r = SetFilePointer((HANDLE)fd, lo_w, &hi_w,
+			   ((whence == SEEK_SET) ? FILE_BEGIN : FILE_END));
+	if ((r == INVALID_SET_FILE_POINTER)
+	    && GetLastError() != NO_ERROR)
           lv = -1;
+	else
+	  lv = 0;
       }
 # else
       lv = BIG_OFF_T_IZE(lseek)(fd, nll, whence);
@@ -4260,11 +4272,14 @@ scheme_file_position(int argc, Scheme_Object *argv[])
     } else if (had_fd) {
 # ifdef WINDOWS_FILE_HANDLES
       {
-        LARGE_INTEGER li;
-        if (!SetFilePointerEx((HANDLE)fd, 0, &li, FILE_CURRENT))
+	DWORD lo_w, hi_w;
+	hi_w = 0;
+        lo_w = SetFilePointer((HANDLE)fd, 0, &hi_w, FILE_CURRENT);
+	if ((lo_w == INVALID_SET_FILE_POINTER)
+	    && GetLastError() != NO_ERROR)
           pll = -1;
         else
-          pll = li;
+          pll = ((mzlonglong)hi_w << 32) | lo_w;
       }
 # else
       pll = BIG_OFF_T_IZE(lseek)(fd, 0, 1);
diff --git a/src/mzscheme/src/read.c b/src/mzscheme/src/read.c
index 31007ead04..641f8835f7 100644
--- a/src/mzscheme/src/read.c
+++ b/src/mzscheme/src/read.c
@@ -5283,7 +5283,7 @@ Scheme_Object *scheme_unmarshal_wrap_get(Scheme_Unmarshal_Tables *ut,
   long l;
   l = SCHEME_INT_VAL(wraps_key);
 
-  if ((l < 0) || (l >= ut->rp->symtab_size))
+  if ((l < 0) || ((unsigned long)l >= ut->rp->symtab_size))
     scheme_ill_formed_code(ut->rp);
 
   if (!ut->rp->symtab[l]) {