diff --git a/radio/src/strhelpers.h b/radio/src/strhelpers.h
index 2ec059137..04fcf58f5 100644
--- a/radio/src/strhelpers.h
+++ b/radio/src/strhelpers.h
@@ -127,7 +127,7 @@ void copyToTerminated(char (&dest)[DL], const char (&src)[SL],
   static_assert(dl > 0, "wrong sizes or offset");
   static constexpr size_t len = (dl < SL) ? dl : SL;
   strncpy(&dest[O], &src[0], len);
-  static_assert((len + O) < DL);
+  static_assert((len + O) < DL, "wrong sizes of offset");
   dest[len + O] = '\0';
 }