diff --git a/libs/image/kis_merge_walker.cc b/libs/image/kis_merge_walker.cc
--- a/libs/image/kis_merge_walker.cc
+++ b/libs/image/kis_merge_walker.cc
@@ -53,27 +53,24 @@
 
 void KisMergeWalker::startTripWithMask(KisProjectionLeafSP filthyMask)
 {
-    if (!filthyMask->parent()) {
-        /**
-         * Under very rare circumstances it may happen that the update
-         * queue will contain a job pointing to a node that has
-         * already been deleted from the image (direclty or by undo
-         * command). If it happens to a layer then the walker will
-         * handle it as usual by building a trivial graph pointing to
-         * nowhere, but when it happens to a mask... not. Because the
-         * mask is always expected to have a parent layer to process.
-         *
-         * So just handle it here separately.
-         */
-
+    /**
+     * Under very rare circumstances it may happen that the update
+     * queue will contain a job pointing to a node that has
+     * already been deleted from the image (direclty or by undo
+     * command). If it happens to a layer then the walker will
+     * handle it as usual by building a trivial graph pointing to
+     * nowhere, but when it happens to a mask... not. Because the
+     * mask is always expected to have a parent layer to process.
+     *
+     * So just handle it here separately.
+     */
+    KisProjectionLeafSP parentLayer = filthyMask->parent();
+    if (!parentLayer) {
         return;
     }
 
     adjustMasksChangeRect(filthyMask);
 
-    KisProjectionLeafSP parentLayer = filthyMask->parent();
-    Q_ASSERT(parentLayer);
-
     KisProjectionLeafSP nextLeaf = parentLayer->nextSibling();
     KisProjectionLeafSP prevLeaf = parentLayer->prevSibling();