diff --git a/src/TimingData.h b/src/TimingData.h
index f64b9054c7..c44b4da58a 100644
--- a/src/TimingData.h
+++ b/src/TimingData.h
@@ -1594,7 +1594,7 @@ public:
 	 */
 	void AddSpeedSegment( const SpeedSegment &seg );
 	
-	float GetDisplayedSpeedPercent( float fBeat, float fMusicSeconds );
+	float GetDisplayedSpeedPercent( float fBeat, float fMusicSeconds ) const;
 	
 	/**
 	 * @brief Determine when the fakes end.