diff --git a/src/builtins/array-join.tq b/src/builtins/array-join.tq
index 84b967fa597..3cd384feb02 100644
--- a/src/builtins/array-join.tq
+++ b/src/builtins/array-join.tq
@@ -467,6 +467,18 @@ transitioning macro ArrayJoinImpl<T: type>(
     if (k > 0) {
       // a. If k > 0, let R be the string-concatenation of R and sep.
       nofSeparators = nofSeparators + 1;
+      // --- POC FAST-FORWARD (testing only; not part of fix) ---------------
+      // The hole-skipping iterations k=1..len-1 each do exactly
+      // `nofSeparators++` and nothing else (element is kEmptyString →
+      // `continue`). Collapsing them by jumping (k, nofSeparators) forward
+      // together is therefore semantically identical to running them. On a
+      // 32-bit target Signed(len-1) == (int32)(len-1), reproducing the wrap
+      // that the real ~4e9-iteration loop produces on native arm32/ia32.
+      if (k == 1 && len > kSmiMaxValue) {
+        nofSeparators = Signed(len - 1);
+        k = len - 1;
+      }
+      // -------------------------------------------------------------------
     }
 
     // b. Let element be ? Get(O, ! ToString(k)).