diff --git a/librocksdb-sys/api/c.cc b/librocksdb-sys/api/c.cc
index bc564c3..9ffe710 100644
--- a/librocksdb-sys/api/c.cc
+++ b/librocksdb-sys/api/c.cc
@@ -3,8 +3,9 @@
 #include "c.h"
 
 static char* CopyString(const std::string& str) {
-  char* result = reinterpret_cast<char*>(malloc(sizeof(char) * str.size()));
+  char* result = reinterpret_cast<char*>(malloc(sizeof(char) * str.size()+1));
   memcpy(result, str.data(), sizeof(char) * str.size());
+  result[sizeof(char) * str.size()] = 0;
   return result;
 }