diff --git a/test/run/idl-ops.mo b/test/run/idl-ops.mo
index bdff4c3417c..6c4bec438a4 100644
--- a/test/run/idl-ops.mo
+++ b/test/run/idl-ops.mo
@@ -51,6 +51,7 @@ assert(null == deserArrayNat (serArrayInt arrayInt));
 assert((?arrayInt) == deserArrayInt (serArrayInt arrayInt));
 let heapDifference = Prim.rts_heap_size() : Int - started_with;
 // Difference between incremental and non-incremental GC
+Prim.debugPrint(debug_show heapDifference);
 assert(heapDifference <= +8_176);
 
 //SKIP run
diff --git a/test/run/idl.mo b/test/run/idl.mo
index 036509ffb4b..4b24c4963bc 100644
--- a/test/run/idl.mo
+++ b/test/run/idl.mo
@@ -44,10 +44,12 @@ assert(arrayNat == deserArrayNat (serArrayNat arrayNat));
 assert(arrayNat == deserArrayInt (serArrayNat arrayNat));
 assert(arrayNat == deserArrayInt (serArrayInt arrayNat));
 assert(arrayInt == deserArrayInt (serArrayInt arrayInt));
-
 let heapDifference = Prim.rts_heap_size() : Int - started_with;
 // Difference between incremental and non-incremental GC
-assert(heapDifference == +4_892 or heapDifference == +5_340);
+assert(heapDifference == 4_488 or // no rtti
+       heapDifference == 4_888 or // no rtti and incremental GC
+       heapDifference == +4_892 or // rtti
+       heapDifference == +5_340);  // rtti and incremental GC
 
 //SKIP run
 //SKIP run-ir