diff --git a/src/sna/sna.h b/src/sna/sna.h
index 34a78812..d8dc4122 100644
--- a/src/sna/sna.h
+++ b/src/sna/sna.h
@@ -623,7 +623,7 @@ static inline bool sna_crtc_is_on(xf86CrtcPtr crtc)
 
 static inline void sna_crtc_set_vblank(xf86CrtcPtr crtc)
 {
-	assert((*sna_crtc_flags(crtc) & CRTC_VBLANK) < 2);
+	assert((*sna_crtc_flags(crtc) & CRTC_VBLANK) < 3);
 	++*sna_crtc_flags(crtc);
 }