Index: src/pmc/slice.pmc
===================================================================
--- src/pmc/slice.pmc	(revision 22482)
+++ src/pmc/slice.pmc	(working copy)
@@ -222,7 +222,9 @@
          * the pointer must not be null, or at the end of iteration and it must
          * point to STRINGs.  Note that r->step is always the integer value 1.
          */
-        if (r && r != -1 && r->type == enum_type_STRING) {
+        if (r &&
+            RVal_int(r->cur) != RVal_int(r->end) &&
+            (r->type == enum_type_STRING)) {
             if (RVal_str(r->start))
                 pobject_lives(INTERP, (PObj *)RVal_str(r->start));
             if (RVal_str(r->end))