diff --git a/src/post_modules/CritBit/tree_source.H b/src/post_modules/CritBit/tree_source.H
index b6b06bd3eb3aec9000aca0b704fe8bdf422964e0..b17faadc329515e900e38ab73f12210e7f9f7b3f 100644
--- a/src/post_modules/CritBit/tree_source.H
+++ b/src/post_modules/CritBit/tree_source.H
@@ -1,3 +1,10 @@
+#ifndef CB_GC_RECURSE_KEY
+# define CB_GC_RECURSE_KEY(X)
+#endif
+#ifndef CB_GC_CHECK_KEY
+# define CB_GC_CHECK_KEY(X)
+#endif
+
     INIT {
 	THIS->tree.root = NULL;
 	THIS->encode_fun = find_identifier
@@ -671,9 +678,7 @@ range_do_clone:
 	if (!node) return;
 	WALK_FORWARD(node, {
 	    if (CB_HAS_VALUE(_)) {
-#ifdef CB_GC_CHECK_KEY
 		CB_GC_CHECK_KEY(_->key);
-#endif
 		debug_gc_check_svalues(&_->value, 1,  " as a CritBit node value");
 	    }
 	});
@@ -684,9 +689,7 @@ range_do_clone:
 	if (!node) return;
 	WALK_FORWARD(node, {
 	    if (CB_HAS_VALUE(_)) {
-#ifdef CB_GC_RECURSE_KEY
 		CB_GC_RECURSE_KEY(_->key);
-#endif
 		gc_recurse_svalues(&_->value, 1);
 	    }
 	});