diff --git a/cstr_util.h b/cstr_util.h
index f7ce853..a5d080b 100644
--- a/cstr_util.h
+++ b/cstr_util.h
@@ -3,6 +3,7 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+#include <stddef.h>
 /**
  * @brief Copy string to another string
  * @param dest The pointer of output string
diff --git a/encoding.cpp b/encoding.cpp
index 2207346..a461b2b 100644
--- a/encoding.cpp
+++ b/encoding.cpp
@@ -30,7 +30,7 @@ bool encoding::iconv_convert(std::string input, std::string& output, std::string
     size_t buf_left = 0;
     std::string out;
     size_t avail_in = input.length();
-    auto in = input.c_str();
+    char* in = (char*)input.c_str();
     if (!buf) {
         iconv_close(cd);
         return false;