diff --git a/source/api_c/include/deepmd.hpp b/source/api_c/include/deepmd.hpp
index 3bb81078c1..1867ac34ad 100644
--- a/source/api_c/include/deepmd.hpp
+++ b/source/api_c/include/deepmd.hpp
@@ -8,6 +8,7 @@ This header-only library provides a C++ 11 interface to the DeePMD-kit C API.
 
 #include <algorithm>
 #include <cassert>
+#include <cstring>
 #include <exception>
 #include <iostream>
 #include <string>
@@ -34,7 +35,7 @@ struct deepmd_exception : public std::runtime_error {
  */
 #define DP_CHECK_OK(check_func, dp)     \
   const char *err_msg = check_func(dp); \
-  if (strlen(err_msg))                  \
+  if (std::strlen(err_msg))             \
     throw deepmd::hpp::deepmd_exception(std::string(err_msg));
 
 template <typename FPTYPE>