diff --git a/vm/gc.cpp b/vm/gc.cpp
index 0de3dac91f..1bb339a70a 100755
--- a/vm/gc.cpp
+++ b/vm/gc.cpp
@@ -230,8 +230,8 @@ struct call_frame_scrubber {
 		gc_info *info = compiled->block_gc_info();
 
 		assert(return_address < compiled->size());
-		int index = info->return_address_index(return_address);
-		if(index != -1)
+		cell index = info->return_address_index(return_address);
+		if(index != (cell)-1)
 			ctx->scrub_stacks(info,index);
 	}
 };
diff --git a/vm/gc_info.hpp b/vm/gc_info.hpp
index eee7b1a8e8..d6bb79f4bd 100644
--- a/vm/gc_info.hpp
+++ b/vm/gc_info.hpp
@@ -1,7 +1,7 @@
 namespace factor
 {
 
-const u32 gc_info_missing_value = (u32)-1;
+const cell gc_info_missing_value = (cell)-1;
 
 struct gc_info {
 	u32 scrub_d_count;
diff --git a/vm/slot_visitor.hpp b/vm/slot_visitor.hpp
index 303fc37544..b97f988e65 100755
--- a/vm/slot_visitor.hpp
+++ b/vm/slot_visitor.hpp
@@ -292,7 +292,7 @@ struct call_frame_slot_visitor {
 		gc_info *info = compiled->block_gc_info();
 
 		assert(return_address < compiled->size());
-		u32 callsite = info->return_address_index(return_address);
+		cell callsite = info->return_address_index(return_address);
 		if(callsite == gc_info_missing_value)
 			return;