diff --git a/stepmania/src/RageUtil.cpp b/stepmania/src/RageUtil.cpp
index 0b50cd5bb4..dfe42a2d3a 100644
--- a/stepmania/src/RageUtil.cpp
+++ b/stepmania/src/RageUtil.cpp
@@ -25,6 +25,15 @@
 
 unsigned long randseed = time(NULL);
 
+/* Return a positive x mod y. */
+float fmodfp(float x, float y)
+{
+	x = fmodf(x, y);	/* x is [-y,y] */
+	x += y;				/* x is [0,y*2] */
+	x = fmodf(x, y);	/* x is [0,y] */
+	return x;
+}
+
 int power_of_two(int input)
 {
     int value = 1;
diff --git a/stepmania/src/RageUtil.h b/stepmania/src/RageUtil.h
index 37c4efc3dd..2470d2c86d 100644
--- a/stepmania/src/RageUtil.h
+++ b/stepmania/src/RageUtil.h
@@ -113,6 +113,9 @@ inline float froundf( const float f, const float fRoundInterval )
 	return int( (f + fRoundInterval/2)/fRoundInterval ) * fRoundInterval;
 }
 
+/* Return a positive x mod y. */
+float fmodfp(float x, float y);
+
 int power_of_two(int input);
 bool IsAnInt( const CString &s );
 bool IsHexVal( const CString &s );