diff --git a/chicken.h b/chicken.h
index 6dfefb9..ce725a4 100644
--- a/chicken.h
+++ b/chicken.h
@@ -1771,6 +1771,7 @@ C_fctexport C_word C_vector(C_word **ptr, int n, ...);
 C_fctexport C_word C_structure(C_word **ptr, int n, ...);
 C_fctexport C_word C_fcall C_mutate_slot(C_word *slot, C_word val) C_regparm;
 C_fctexport C_word C_fcall C_mutate(C_word *slot, C_word val) C_regparm;
+C_fctexport C_word C_fcall  C_check_heap_consistency(C_word dummy) C_regparm;
 C_fctexport void C_fcall C_reclaim(void *trampoline, void *proc) C_regparm C_noret;
 C_fctexport void C_save_and_reclaim(void *trampoline, void *proc, int n, ...) C_noret;
 C_fctexport void C_fcall C_rereclaim2(C_uword size, int double_plus) C_regparm;
diff --git a/library.scm b/library.scm
index 59ddc36..961714c 100644
--- a/library.scm
+++ b/library.scm
@@ -5162,3 +5162,7 @@ EOF
       (loop (- len 1) (cdr input)))
      (else input))))
 
+
+;;;
+
+(define (##sys#check-heap-consistency) (##core#inline "C_check_heap_consistency" #f))
diff --git a/runtime.c b/runtime.c
index f68cd09..006b7af 100644
--- a/runtime.c
+++ b/runtime.c
@@ -3123,6 +3123,69 @@ C_regparm void C_fcall C_reclaim(void *trampoline, void *proc)
 }
 
 
+C_regparm C_word C_fcall C_check_heap_consistency(C_word dummy)
+{
+  C_word n, bytes, *p, x;
+  C_header h;
+  int i, f = 0;
+  C_SCHEME_BLOCK *bp = (C_SCHEME_BLOCK *)fromspace_start;
+
+  while((C_byte *)bp < C_fromspace_top) {
+    if(*((C_word *)bp) == ALIGNMENT_HOLE_MARKER) 
+      bp = (C_SCHEME_BLOCK *)((C_word *)bp + 1);
+
+    n = C_header_size(bp);
+    h = bp->header;
+    bytes = (h & C_BYTEBLOCK_BIT) ? n : n * sizeof(C_word);
+    p = bp->data;
+    i = 0;
+
+    if(n > 0 && (h & C_BYTEBLOCK_BIT) == 0) {
+      if(h & C_SPECIALBLOCK_BIT) {
+	--n;
+        ++i;
+	++p;
+      }
+
+      while(n--) {
+        x = *(p++);
+
+        if(!C_immediatep(x)) {
+          if((C_block_header(x) & C_GC_FORWARDING_BIT) != 0) {
+            if(!f) {
+              C_fputc('\n', C_stderr);
+              f = 1;
+            }
+
+            fprintf(C_stderr, C_text("Invalid forwarded object-pointer: [object=" UWORD_FORMAT_STRING
+                                     ", header=" UWORD_FORMAT_STRING
+                                     ": index=" UWORD_COUNT_FORMAT_STRING ", pointer=" UWORD_FORMAT_STRING "]\n"),
+                    (C_uword)bp, (C_uword)h, i, (C_uword)x);
+          }
+          else if(C_in_heapp(x) && !C_in_fromspacep(x)) {
+            if(!f) {
+              C_fputc('\n', C_stderr);
+              f = 1;
+            }
+
+            fprintf(C_stderr, C_text("Invalid non-heap object-pointer: [object=" UWORD_FORMAT_STRING
+                                     ", header=" UWORD_FORMAT_STRING
+                                     ": index=" UWORD_COUNT_FORMAT_STRING ", pointer=" UWORD_FORMAT_STRING "]\n"),
+                    (C_uword)bp, (C_uword)h, i, (C_uword)x);
+          }
+        }
+
+        ++i;
+      }
+    }
+
+    bp = (C_SCHEME_BLOCK *)((C_byte *)bp + C_align(bytes) + sizeof(C_header));
+  }
+
+  return C_mk_bool(f);
+}
+
+
 C_regparm void C_fcall mark_system_globals(void)
 {
   mark(&interrupt_hook_symbol);
diff --git a/tests/lolevel-tests.scm b/tests/lolevel-tests.scm
index 3a1dc70..4c41cbe 100644
--- a/tests/lolevel-tests.scm
+++ b/tests/lolevel-tests.scm
@@ -217,6 +217,7 @@
 (define ev-tstvec (object-evict tstvec))
 (assert (not (eq? tstvec ev-tstvec)))
 (assert (object-evicted? ev-tstvec))
+(set! ev-tstvec #f)
 (object-release ev-tstvec)
 
 ; object-evict-to-location