diff --git a/src/interpreter_extra.cc b/src/interpreter_extra.cc
index 20d1fb9..a536b0e 100644
--- a/src/interpreter_extra.cc
+++ b/src/interpreter_extra.cc
@@ -1542,7 +1542,7 @@ static void opTileDistanceBetweenObjects(Program* program)
 
     int distance = 9999;
     if (object1 != NULL && object2 != NULL) {
-        if ((intptr_t)object2 >= HEX_GRID_SIZE && (intptr_t)object1 >= HEX_GRID_SIZE) {
+        if ((uintptr_t)object2 >= HEX_GRID_SIZE && (uintptr_t)object1 >= HEX_GRID_SIZE) {
             if (object1->elevation == object2->elevation) {
                 if (object1->tile != -1 && object2->tile != -1) {
                     distance = tileDistanceBetween(object1->tile, object2->tile);