diff --git a/linux-core/drm_irq.c b/linux-core/drm_irq.c
index 57419ca..89da0b9 100644
--- a/linux-core/drm_irq.c
+++ b/linux-core/drm_irq.c
@@ -541,6 +541,16 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
 		return ret;
 	seq = drm_vblank_count(dev, crtc);
 
+	if (dev->vblank_inmodeset[crtc]) {
+		if (flags & _DRM_VBLANK_SIGNAL)
+			ret = -EBUSY;
+		else {
+			vblwait->request.type &= ~_DRM_VBLANK_RELATIVE;
+			vblwait->reply.sequence = seq;
+		}
+		goto done;
+	}
+
 	switch (vblwait->request.type & _DRM_VBLANK_TYPES_MASK) {
 	case _DRM_VBLANK_RELATIVE:
 		vblwait->request.sequence += seq;