diff --git a/source/simple/file.hpp b/source/simple/file.hpp
index c5989d7e93debd5f93f9460127df6e6664603dcd..dd2daffc630b057ede9914fd328816a26b2758ef 100644
--- a/source/simple/file.hpp
+++ b/source/simple/file.hpp
@@ -167,7 +167,7 @@ namespace string_stack
 	}
 
 	// supa slow way
-	std::streamsize defined_size(stream& file)
+	inline std::streamsize defined_size(stream& file)
 	{
 		file.ignore( std::numeric_limits<std::streamsize>::max() );
 		std::streamsize size = file.gcount();