diff --git a/src/string-format-check.cpp b/src/string-format-check.cpp
index ce69396..bd8952f 100644
--- a/src/string-format-check.cpp
+++ b/src/string-format-check.cpp
@@ -1,6 +1,6 @@
 #include <nlohmann/json-schema.hpp>
 
-#include <smtp-address-validator.hpp>
+#include "smtp-address-validator.hpp"
 
 #include <algorithm>
 #include <exception>