Index: source/blender/blenkernel/intern/cdderivedmesh.c
===================================================================
--- source/blender/blenkernel/intern/cdderivedmesh.c	(revision 47539)
+++ source/blender/blenkernel/intern/cdderivedmesh.c	(working copy)
@@ -415,16 +418,24 @@
 	
 	if (GPU_buffer_legacy(dm)) {
 		DEBUG_VBO("Using legacy code. cdDM_drawEdges\n");
		glBegin(GL_LINES);
 		for (i = 0; i < dm->numEdgeData; i++, medge++) {
-			if ((drawAllEdges || (medge->flag & ME_EDGEDRAW)) &&
-			    (drawLooseEdges || !(medge->flag & ME_LOOSEEDGE)))
-			{
-				glVertex3fv(mvert[medge->v1].co);
-				glVertex3fv(mvert[medge->v2].co);
+			#define is_visible     (drawAllEdges   ||  (medge->flag & ME_EDGEDRAW))
+			#define is_not_loose   (drawLooseEdges || !(medge->flag & ME_LOOSEEDGE))
+			#define is_interesting (medge->flag & (ME_SEAM|ME_SHARP))
+
+			if ((is_visible && is_not_loose) || is_interesting) {
+				gpuVertex3fv(mvert[medge->v1].co);
+				gpuVertex3fv(mvert[medge->v2].co);
 			}
+
+			#undef is_visible
+			#undef is_not_loose
+			#undef is_interesting
 		}
		glEnd();
 	}
 	else {  /* use OpenGL VBOs or Vertex Arrays instead for better, faster rendering */
 		int prevstart = 0;