diff --git a/src/duk_error.h b/src/duk_error.h
index 63591687..99c54c78 100644
--- a/src/duk_error.h
+++ b/src/duk_error.h
@@ -16,7 +16,7 @@
 #define DUK_ERROR_H_INCLUDED
 
 /*
- *  Error codes (defined in duktape.h)
+ *  Error codes: defined in duktape.h
  *
  *  Error codes are used as a shorthand to throw exceptions from inside
  *  the implementation.  The appropriate Ecmascript object is constructed
@@ -25,11 +25,6 @@
  *  by calling code.
  */
 
-/* FIXME: remove */
-/* for function return codes */
-#define DUK_ERR_OK                   0     /* call successful */
-#define DUK_ERR_FAIL                 1     /* call failed */
-
 /*
  *  Normal error
  *
diff --git a/src/duk_heap_markandsweep.c b/src/duk_heap_markandsweep.c
index a8da72b2..8688e1b9 100644
--- a/src/duk_heap_markandsweep.c
+++ b/src/duk_heap_markandsweep.c
@@ -887,7 +887,7 @@ int duk_heap_mark_and_sweep(duk_heap *heap, int flags) {
 #ifdef DUK_USE_VOLUNTARY_GC
 		heap->mark_and_sweep_trigger_counter = DUK_HEAP_MARK_AND_SWEEP_TRIGGER_SKIP;
 #endif
-		return DUK_ERR_OK;
+		return 0;  /* OK */
 	}
 
 	DUK_DPRINT("garbage collect (mark-and-sweep) starting, requested flags: 0x%08x, effective flags: 0x%08x",
@@ -1077,7 +1077,7 @@ int duk_heap_mark_and_sweep(duk_heap *heap, int flags) {
 	DUK_DPRINT("garbage collect (mark-and-sweep) finished: %d objects kept, %d strings kept, no voluntary trigger",
 	           (int) count_keep_obj, (int) count_keep_str);
 #endif
-	return DUK_ERR_OK;
+	return 0;  /* OK */
 }
 
 #else  /* DUK_USE_MARK_AND_SWEEP */
diff --git a/src/duk_heap_stringtable.c b/src/duk_heap_stringtable.c
index d974a3ba..ca7c1fef 100644
--- a/src/duk_heap_stringtable.c
+++ b/src/duk_heap_stringtable.c
@@ -267,11 +267,11 @@ static int duk__resize_strtab_raw(duk_heap *heap, duk_uint32_t new_size) {
 	heap->st_size = new_size;
 	heap->st_used = new_used;  /* may be less, since DELETED entries are NULLed by rehash */
 
-	return DUK_ERR_OK;
+	return 0;  /* OK */
 
  error:
 	DUK_FREE(heap, new_entries);
-	return DUK_ERR_FAIL;
+	return 1;  /* FAIL */
 }
 
 static int duk__resize_strtab(duk_heap *heap) {
@@ -314,7 +314,7 @@ static int duk__recheck_strtab_size(duk_heap *heap, duk_uint32_t new_used) {
 		/* load factor too low or high, count actually used entries and resize */
 		return duk__resize_strtab(heap);
 	} else {
-		return DUK_ERR_OK;
+		return 0;  /* OK */
 	}
 }