diff --git a/mps/code/abq.h b/mps/code/abq.h
index 7a7cc2a65d9..022fc7e5301 100644
--- a/mps/code/abq.h
+++ b/mps/code/abq.h
@@ -29,9 +29,9 @@ typedef Bool (*ABQIterateMethod)(Bool *deleteReturn, void *element, void *closur
 extern Res ABQInit(Arena arena, ABQ abq, void *owner, Count elements, Size elementSize);
 extern Bool ABQCheck(ABQ abq);
 extern void ABQFinish(Arena arena, ABQ abq);
-extern Res ABQPush(ABQ abq, void *element);
-extern Res ABQPop(ABQ abq, void *elementReturn);
-extern Res ABQPeek(ABQ abq, void *elementReturn);
+extern Bool ABQPush(ABQ abq, void *element);
+extern Bool ABQPop(ABQ abq, void *elementReturn);
+extern Bool ABQPeek(ABQ abq, void *elementReturn);
 extern Res ABQDescribe(ABQ abq, ABQDescribeElement describeElement, mps_lib_FILE *stream);
 extern Bool ABQIsEmpty(ABQ abq);
 extern Bool ABQIsFull(ABQ abq);