diff --git a/src/cryptaux.hxx b/src/cryptaux.hxx
index e186608..48a1dc8 100644
--- a/src/cryptaux.hxx
+++ b/src/cryptaux.hxx
@@ -179,7 +179,7 @@ namespace crypto {
 
   /// convert integer to binary of given size
   inline std::string toBinary(unsigned long data, int bytes=2) {
-    std::string res('\0', bytes);
+    std::string res(bytes, '\0');
     for (int i(0); i<bytes; ++i) {
       res[i] = std::string::value_type(data&0xff);
       data>>=8;