diff --git a/src/paramdict.cpp b/src/paramdict.cpp
index 4704ea169e6..0bbfb467824 100644
--- a/src/paramdict.cpp
+++ b/src/paramdict.cpp
@@ -555,7 +555,15 @@ int ParamDict::load_param_bin(const DataReader& dr)
 
             tmpstr[len_padded] = '\0';
 
+#if NCNN_SIMPLESTL
+            // simple stl string has no tail zero by default, append one
+            d->params[id].s.resize(len + 1);
+            memcpy(d->params[id].s.data(), tmpstr.data(), len);
+            d->params[id].s[len] = '\0';
+            d->params[id].s.resize(len);
+#else
             d->params[id].s = tmpstr.data();
+#endif
 
             d->params[id].type = 7;
         }