diff --git a/src/kit/shell/shellCommand.c b/src/kit/shell/shellCommand.c
index 72e669d8b29a398d3542e56b2f0e8e510d0f120c..70abc7b43c0477e64a980a5deb1e212a0097d317 100644
--- a/src/kit/shell/shellCommand.c
+++ b/src/kit/shell/shellCommand.c
@@ -57,7 +57,8 @@ void getPrevCharSize(const char *str, int pos, int *size, int *width) {
     if (str[pos] > 0 || countPrefixOnes(str[pos]) > 1) break;
   }
 
-  assert(mbtowc(&wc, str + pos, MB_CUR_MAX) == *size);
+  int rc = mbtowc(&wc, str + pos, MB_CUR_MAX);
+  assert(rc == *size);
 
   *width = wcwidth(wc);
 }