diff --git a/include/minikin/SystemFonts.h b/include/minikin/SystemFonts.h
index 4ef2705..518eb10 100644
--- a/include/minikin/SystemFonts.h
+++ b/include/minikin/SystemFonts.h
@@ -17,6 +17,7 @@
 #ifndef MINIKIN_SYSTEM_FONTS_H
 #define MINIKIN_SYSTEM_FONTS_H
 
+#include <functional>
 #include <map>
 #include <memory>
 #include <mutex>