diff --git a/src/core/utf8.hpp b/src/core/utf8.hpp
index db1354ef24..26e6305ba9 100644
--- a/src/core/utf8.hpp
+++ b/src/core/utf8.hpp
@@ -13,11 +13,17 @@
 #define UTF8_HPP
 
 #include <iterator>
-#include "../string_func.h"
+#include "bitmath_func.hpp"
 
 [[nodiscard]] std::pair<char[4], size_t> EncodeUtf8(char32_t c);
 [[nodiscard]] std::pair<size_t, char32_t> DecodeUtf8(std::string_view buf);
 
+/* Check if the given character is part of a UTF8 sequence */
+inline bool IsUtf8Part(char c)
+{
+	return GB(c, 6, 2) == 2;
+}
+
 /**
  * Constant span of UTF-8 encoded data.
  */
diff --git a/src/string_func.h b/src/string_func.h
index c7e8910542..9fa5636204 100644
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -72,13 +72,6 @@ inline bool StrEmpty(const char *s)
 
 bool IsValidChar(char32_t key, CharSetFilter afilter);
 
-
-/* Check if the given character is part of a UTF8 sequence */
-inline bool IsUtf8Part(char c)
-{
-	return GB(c, 6, 2) == 2;
-}
-
 size_t Utf8StringLength(std::string_view str);
 
 /**