diff --git a/mecab/src/writer.cpp b/mecab/src/writer.cpp
index a7873d77..5fc4e83d 100644
--- a/mecab/src/writer.cpp
+++ b/mecab/src/writer.cpp
@@ -252,7 +252,8 @@ bool Writer::writeNode(Lattice *lattice,
       case '%': {  // macros
         switch (*++p) {
           default: {
-            const std::string error = "unknown meta char: " + *p;
+            std::string error = "unknown meta char: ";
+            error += *p;
             lattice->set_what(error.c_str());
             return false;
           }