diff --git a/source/blender/src/editmesh.c b/source/blender/src/editmesh.c
index b7179dd0c16..98426a6a7a8 100644
--- a/source/blender/src/editmesh.c
+++ b/source/blender/src/editmesh.c
@@ -1407,6 +1407,7 @@ void separate_mesh(void)
 	emcopy.allverts= NULL;
 	emcopy.alledges= NULL;
 	emcopy.allfaces= NULL;
+	emcopy.derived= NULL;
 	free_editMesh(&emcopy);
 	
 	em->verts= edve;