diff --git a/include/utf8proc.h b/include/utf8proc.h
index 0dfe537..692d935 100644
--- a/include/utf8proc.h
+++ b/include/utf8proc.h
@@ -224,6 +224,7 @@ static inline utf8proc_ssize_t utf8proc_encode_char(utf8proc_int32_t uc, utf8pro
 
 #ifdef __cplusplus
 #include <iterator>
+#include <string>
 
 class UTF8Iterator : public std::iterator<std::forward_iterator_tag, uint32_t>
 {