diff --git a/sys/dev/drm/i915/intel_hangcheck.c b/sys/dev/drm/i915/intel_hangcheck.c
--- a/sys/dev/drm/i915/intel_hangcheck.c
+++ b/sys/dev/drm/i915/intel_hangcheck.c
@@ -119,7 +119,7 @@
 	if (!i)
 		return NULL;
 
-	*seqno = ioread32(vaddr + head + 4) + 1;
+	*seqno = ioread32(vaddr + ((head + 4) & (engine->buffer->size - 1))) + 1;
 	return semaphore_wait_to_signaller_ring(engine, ipehr, offset);
 }