diff --git a/src/crypto/crypto.c b/src/crypto/crypto.c
index a461ef9..d9f1a4e 100644
--- a/src/crypto/crypto.c
+++ b/src/crypto/crypto.c
@@ -632,7 +632,7 @@
         return NULL;
     }
 
-    buffer = PyString_FromStringAndSize(sig_buf, sig_len);
+    buffer = PyString_FromStringAndSize((char*)sig_buf, sig_len);
     return buffer;
 }