Do not optimize lines away entirely

src/ol/render/canvas/canvasreplay.js

@@ -489,7 +489,7 @@ ol.render.canvas.Replay.prototype.replay_ = function(
           y = pixelCoordinates[d + 1];
           roundX = (x + 0.5) | 0;
           roundY = (y + 0.5) | 0;
-          if (roundX !== prevX || roundY !== prevY) {
+          if (d == dd - 2 || roundX !== prevX || roundY !== prevY) {
             context.lineTo(x, y);
             prevX = roundX;
             prevY = roundY;

test_rendering/spec/ol/layer/vector.test.js

@@ -49,6 +49,15 @@ describe('ol.rendering.layer.Vector', function() {
 
     it('renders correctly with the canvas renderer', function(done) {
       map = createMap('canvas');
+      var smallLine = new ol.Feature(new ol.geom.LineString([
+        [center[0], center[1] - 1],
+        [center[0], center[1] + 1]
+      ]));
+      smallLine.setStyle(new ol.style.Style({
+        zIndex: -99,
+        stroke: new ol.style.Stroke({width: 75, color: 'red'})
+      }));
+      source.addFeature(smallLine);
       addPolygon(100);
       addCircle(200);
       addPolygon(250);