diff --git a/include/easypr/program_options.h b/include/easypr/program_options.h
index 3789245..00fd67b 100644
--- a/include/easypr/program_options.h
+++ b/include/easypr/program_options.h
@@ -9,6 +9,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <cstring>
 #include <iostream>
 #include <map>
 #include <string>
@@ -351,4 +352,4 @@ class Parser {
 
 }
 
-#endif // UTIL_PROGRAM_OPTIONS_H
\ No newline at end of file
+#endif // UTIL_PROGRAM_OPTIONS_H