diff --git a/src/mzscheme/gc2/weak.c b/src/mzscheme/gc2/weak.c
index f8644a200c..4e68b4567f 100644
--- a/src/mzscheme/gc2/weak.c
+++ b/src/mzscheme/gc2/weak.c
@@ -63,7 +63,7 @@ static int mark_weak_array(void *p)
     for (i = a->count; i--; ) {
       if (data[i] 
 	  && (*(short *)(data[i]) != 45)
-	  && (*(short *)(data[i]) != 54))
+	  && (*(short *)(data[i]) != 55))
 	CRASH(1);
     }
   }
diff --git a/src/mzscheme/src/env.c b/src/mzscheme/src/env.c
index 666c12c791..575d1b3fc6 100644
--- a/src/mzscheme/src/env.c
+++ b/src/mzscheme/src/env.c
@@ -276,6 +276,14 @@ Scheme_Env *scheme_basic_env()
     }
   }
 
+#ifdef MZ_PRECISE_GC
+  scheme_register_traversers();
+  register_traversers();
+  scheme_init_hash_key_procs();
+#endif
+
+  scheme_init_true_false();
+
   REGISTER_SO(toplevels_ht);
   REGISTER_SO(locals_ht[0]);
   REGISTER_SO(locals_ht[1]);
@@ -289,14 +297,6 @@ Scheme_Env *scheme_basic_env()
     locals_ht[1] = ht;
   }
 
-  scheme_init_true_false();
-
-#ifdef MZ_PRECISE_GC
-  scheme_register_traversers();
-  register_traversers();
-  scheme_init_hash_key_procs();
-#endif
-
 #ifdef TIME_STARTUP_PROCESS
   printf("pre-process @ %ld\n", scheme_get_process_milliseconds());
 #endif
diff --git a/src/mzscheme/src/port.c b/src/mzscheme/src/port.c
index 967066bf41..8072390c98 100644
--- a/src/mzscheme/src/port.c
+++ b/src/mzscheme/src/port.c
@@ -1379,8 +1379,7 @@ long scheme_get_byte_string_unless(const char *who,
       unsigned char *s;
 
       i = ip->ungotten_count;
-      s = (unsigned char *)ip->ungotten;
-      /* s is in reverse order */
+      /* s will be in reverse order */
 
       if (peek) {
 	if (!SCHEME_INTP(peek_skip) || (i < SCHEME_INT_VAL(peek_skip))) {
@@ -1398,9 +1397,11 @@ long scheme_get_byte_string_unless(const char *who,
 	l = size;
 
       size -= l;
+      s = (unsigned char *)ip->ungotten; /* Not GC-safe! */
       while (l--) {
 	buffer[offset + got++] = s[--i];
       }
+      s = NULL;
 
       if (!peek)
 	ip->ungotten_count = i;