1 files changed, 5 insertions, 2 deletions
diff --git a/misc.c b/misc.c
index 5b10feeb..52567b7d 100644
--- a/misc.c
+++ b/misc.c
@@ -246,7 +246,7 @@ void *arg2;
     	byte_sz = WORDS_TO_BYTES(word_sz);
 	if (GC_all_interior_pointers) {
 	    /* We need one extra byte; don't fill in GC_size_map[byte_sz] */
-	    byte_sz--;
+	    byte_sz -= EXTRA_BYTES;
 	}
 
     	for (j = low_limit; j <= byte_sz; j++) GC_size_map[j] = word_sz;  
@@ -804,7 +804,10 @@ void GC_init_inner()
 
 void GC_enable_incremental GC_PROTO(())
 {
-# if !defined(SMALL_CONFIG)
+# if !defined(SMALL_CONFIG) && !defined(KEEP_BACK_PTRS)
+  /* If we are keeping back pointers, the GC itself dirties all	*/
+  /* pages on which objects have been marked, making 		*/
+  /* incremental GC pointless.					*/
   if (!GC_find_leak) {
     DCL_LOCK_STATE;