diff --git a/flash.hpp b/flash.hpp
index dc27bec..9cfd8e1 100644
--- a/flash.hpp
+++ b/flash.hpp
@@ -2,7 +2,7 @@
 
 #include <avr/pgmspace.h>
 
-#define F(str) (reinterpret_cast<const detail::FlashString *>(PSTR(str)))
+#define F(str) (reinterpret_cast<const ::detail::FlashString *>(PSTR(str)))
 
 namespace detail {