diff --git a/src/builtin_functions.c b/src/builtin_functions.c
index 21eadca473ba79209a2d237712b16f1f8fabb802..53ab05abf7378a72c3c3effec619c5b53b7a43a7 100644
--- a/src/builtin_functions.c
+++ b/src/builtin_functions.c
@@ -1238,10 +1238,12 @@ PMOD_EXPORT void f_has_prefix(INT32 args)
     CASE_SHIFT(1,0);
     CASE_SHIFT(2,0);
     CASE_SHIFT(2,1);
+#ifdef PIKE_DEBUG
   default:
     Pike_error("Unexpected string shift combination: a:%d, b:%d!\n",
 	  a->size_shift, b->size_shift);
     break;
+#endif
   }
 #undef CASE_SHIFT
 #undef TWO_SHIFTS
@@ -1312,10 +1314,12 @@ PMOD_EXPORT void f_has_suffix(INT32 args)
     CASE_SHIFT(1,0);
     CASE_SHIFT(2,0);
     CASE_SHIFT(2,1);
+#ifdef PIKE_DEBUG
   default:
     Pike_error("Unexpected string shift combination: a:%d, b:%d!\n",
 	  a->size_shift, b->size_shift);
     break;
+#endif
   }
 #undef CASE_SHIFT
 #undef TWO_SHIFTS