diff --git a/src/eval.cpp b/src/eval.cpp
index 0a34b13..997aeef 100644
--- a/src/eval.cpp
+++ b/src/eval.cpp
@@ -473,7 +473,7 @@ namespace Slime {
                         Globals::Current_Execution.nass.reserve(pc->value.continuation->nass.next_index);
                         Globals::Current_Execution.nass.next_index = pc->value.continuation->nass.next_index;
 
-                        for (int i = 0; i < pc->value.continuation->nass.next_index; ++i) {
+                        for (u32 i = 0; i < pc->value.continuation->nass.next_index; ++i) {
                             Globals::Current_Execution.nass.data[i].alloc();
                             for (Globals::Current_Execution.nass.data[i].next_index = 0;
                                  Globals::Current_Execution.nass.data[i].next_index < pc->value.continuation->nass.data[i].next_index;)