diff --git a/source/blender/blenkernel/intern/editderivedmesh.c b/source/blender/blenkernel/intern/editderivedmesh.c
index 89bf06be07e..b11d87b1557 100644
--- a/source/blender/blenkernel/intern/editderivedmesh.c
+++ b/source/blender/blenkernel/intern/editderivedmesh.c
@@ -173,7 +173,7 @@ static void BMEdit_RecalcTesselation_intern(BMEditMesh *tm)
 			l = BMIter_New(&liter, bm, BM_LOOPS_OF_FACE, f);
 			for (j=0; l; l=BMIter_Step(&liter), j++) {
 				/*mark order*/
-				l->_index = j;
+				BM_SetIndex(l, j); /* set_loop */
 
 				v = BLI_addfillvert(l->v->co);
 				v->tmp.p = l;
@@ -198,9 +198,9 @@ static void BMEdit_RecalcTesselation_intern(BMEditMesh *tm)
 
 				BLI_array_growone(looptris);
 
-				if (l1->_index > l2->_index) { SWAP(BMLoop*, l1, l2); }
-				if (l2->_index > l3->_index) { SWAP(BMLoop*, l2, l3); }
-				if (l1->_index > l2->_index) { SWAP(BMLoop*, l1, l2); }
+				if (BM_GetIndex(l1) > BM_GetIndex(l2)) { SWAP(BMLoop*, l1, l2); }
+				if (BM_GetIndex(l2) > BM_GetIndex(l3)) { SWAP(BMLoop*, l2, l3); }
+				if (BM_GetIndex(l1) > BM_GetIndex(l2)) { SWAP(BMLoop*, l1, l2); }
 
 				looptris[i][0] = l1;
 				looptris[i][1] = l2;
diff --git a/source/blender/bmesh/bmesh_class.h b/source/blender/bmesh/bmesh_class.h
index ddfdf775671..081a5782939 100644
--- a/source/blender/bmesh/bmesh_class.h
+++ b/source/blender/bmesh/bmesh_class.h
@@ -37,13 +37,10 @@ struct BMVert;
 struct BMEdge;
 struct BMLoop;
 struct BMFace;
-struct BMVert;
-struct BMEdge;
-struct BMLoop;
-struct BMFace;
+struct BMFlagLayer;
 struct BMLayerType;
 struct BMSubClassLayer;
-struct BMFlagLayer;
+
 struct BLI_mempool;
 struct Object;
 
@@ -54,7 +51,12 @@ struct Object;
 typedef struct BMHeader {
 	void *data; /*customdata layers*/
 	struct BMFlagLayer *flags;
-	int index; /*note: use BM_GetIndex/SetIndex macros for index*/
+	int index; /* notes:
+	            * - Use BM_GetIndex/SetIndex macros for index
+	            * - Unitialized to -1 so we can easily tell its not set.
+	            * - Used for edge/vert/face, check BMesh.elem_index_dirty for valid index values,
+	            *   this is abused by various tools which set it dirty.
+	            * - For loops this is used for sorting during tesselation. */
 
 	char htype; /*element geometric type (verts/edges/loops/faces)*/
 	char hflag; /*this would be a CD layer, see below*/
@@ -95,7 +97,6 @@ typedef struct BMLoop {
 	
 	/*private variables*/
 	struct BMLoop *next, *prev; /*won't be able to use listbase API, ger, due to head*/
-	int _index; /*used for sorting during tesselation*/
 } BMLoop;
 
 /*eventually, this structure will be used for supporting holes in faces*/
diff --git a/source/blender/bmesh/operators/bevel.c b/source/blender/bmesh/operators/bevel.c
index e9f6677a6c8..3b60a3cbd8f 100644
--- a/source/blender/bmesh/operators/bevel.c
+++ b/source/blender/bmesh/operators/bevel.c
@@ -199,7 +199,7 @@ void bmesh_bevel_exec(BMesh *bm, BMOperator *op)
 					continue;
 			
 				BM_ITER(l2, &liter2, bm, BM_LOOPS_OF_FACE, l->f) {
-					BM_SetIndex(l2, BLI_array_count(tags)); /* set_dirty! */
+					BM_SetIndex(l2, BLI_array_count(tags)); /* set_loop */
 					BLI_array_growone(tags);
 
 					if (!BMO_TestFlag(bm, l2->e, EDGE_OLD)) {