diff --git a/source/blender/blenkernel/intern/subsurf_ccg.c b/source/blender/blenkernel/intern/subsurf_ccg.c
index 12d7409..5607170 100644
--- a/source/blender/blenkernel/intern/subsurf_ccg.c
+++ b/source/blender/blenkernel/intern/subsurf_ccg.c
@@ -1436,7 +1436,8 @@ static void ccgdm_getVertCos(DerivedMesh *dm, float (*cos)[3])
 	CCGEdge **edgeMap2;
 	CCGVert **vertMap2;
 	int index, totvert, totedge, totface;
-	
+
+	BLI_lock_thread(LOCK_CUSTOM1);
 	totvert = ccgSubSurf_getNumVerts(ss);
 	vertMap2 = MEM_mallocN(totvert * sizeof(*vertMap2), "vertmap");
 	for (vi = ccgSubSurf_getVertIterator(ss); !ccgVertIterator_isStopped(vi); ccgVertIterator_next(vi)) {
@@ -1464,6 +1465,8 @@ static void ccgdm_getVertCos(DerivedMesh *dm, float (*cos)[3])
 	}
 	ccgFaceIterator_free(fi);
 
+	BLI_unlock_thread(LOCK_CUSTOM1);
+
 	i = 0;
 	for (index = 0; index < totface; index++) {
 		CCGFace *f = faceMap2[index];