--- src/mouse.c	2009-03-07 18:39:08.000000000 -0800
+++ src/mouse.c	2009-03-07 18:46:48.000000000 -0800
@@ -2156,7 +2156,10 @@
 
     if (pMse->emulateWheel) {
 	/* Emulate wheel button handling */
-	wheelButtonMask = 1 << (pMse->wheelButton - 1);
+ 	if(pMse->wheelButton == 0)
+ 	    wheelButtonMask = 0;
+ 	else
+	    wheelButtonMask = 1 << (pMse->wheelButton - 1);
 
 	if (change & wheelButtonMask) {
 	    if (buttons & wheelButtonMask) {
@@ -2179,7 +2182,7 @@
 	    ms = pMse->wheelButtonExpires - GetTimeInMillis ();
 
 	/* Intercept wheel emulation. */
-	if (buttons & wheelButtonMask) {
+	if ((buttons & wheelButtonMask) || wheelButtonMask==0) {
 	    if (ms <= 0) {
 		/* Y axis movement */
 		if (pMse->negativeY != MSE_NOAXISMAP) {
@@ -2195,6 +2198,7 @@
 		    while (abs(pMse->wheelYDistance) > pMse->wheelInertia) {
 			pMse->wheelYDistance -= emuWheelDelta;
 
+ 			pMse->wheelXDistance = 0;
 			/*
 			 * Synthesize the press and release, but not when
 			 * the button to be synthesized is already pressed
@@ -2222,6 +2226,7 @@
 		    while (abs(pMse->wheelXDistance) > pMse->wheelInertia) {
 			pMse->wheelXDistance -= emuWheelDelta;
 
+ 			pMse->wheelYDistance = 0;
 			/*
 			 * Synthesize the press and release, but not when
 			 * the button to be synthesized is already pressed