diff --git a/Testing/printDebugging.h b/Testing/printDebugging.h
index d6b4d9f..1dd12e2 100644
--- a/Testing/printDebugging.h
+++ b/Testing/printDebugging.h
@@ -35,7 +35,7 @@ namespace Alepha::Hydrogen::Testing  ::detail::  printDebugging_m
 		enum class OutputMode { All, Relaxed };
 
 		template< OutputMode outputMode, typename T >
-		void streamDebugging( const T &witness, const T &expected );
+		void streamDebugging( std::ostream &stream, const T &witness, const T &expected );
 
 		template< OutputMode outputMode, typename T >
 		void printDebugging( const T &witness, const T &expected );