diff --git a/src/core/def.c b/src/core/def.c
index e37501ae..514e701e 100644
--- a/src/core/def.c
+++ b/src/core/def.c
@@ -183,7 +183,8 @@ lwip_strnicmp(const char *str1, const char *str2, size_t len)
         return 1;
       }
     }
-  } while (len-- && c1 != 0);
+    len--;
+  } while ((len != 0) && (c1 != 0));
   return 0;
 }
 #endif