diff --git a/hw/xfree86/modes/xf86Crtc.c b/hw/xfree86/modes/xf86Crtc.c
index dd8ccad4a..30742ff2e 100644
--- a/hw/xfree86/modes/xf86Crtc.c
+++ b/hw/xfree86/modes/xf86Crtc.c
@@ -2976,6 +2976,8 @@ xf86OutputSetEDID (xf86OutputPtr output, xf86MonPtr edid_mon)
 	free(output->MonInfo);
     
     output->MonInfo = edid_mon;
+    output->mm_width = 0;
+    output->mm_height = 0;
 
     if (debug_modes) {
 	xf86DrvMsg(scrn->scrnIndex, X_INFO, "EDID for output %s\n",