diff --git a/src/ol/renderer/canvas/canvasimagelayerrenderer.js b/src/ol/renderer/canvas/canvasimagelayerrenderer.js
index afbaebfbf4..6fad17913b 100644
--- a/src/ol/renderer/canvas/canvasimagelayerrenderer.js
+++ b/src/ol/renderer/canvas/canvasimagelayerrenderer.js
@@ -111,7 +111,7 @@ ol.renderer.canvas.ImageLayer.prototype.prepareFrame =
       !ol.extent.isEmpty(renderedExtent)) {
     var projection = viewState.projection;
     var sourceProjection = imageSource.getProjection();
-    if (goog.isDefAndNotNull(sourceProjection)) {
+    if (!goog.isNull(sourceProjection)) {
       goog.asserts.assert(ol.proj.equivalent(projection, sourceProjection));
       projection = sourceProjection;
     }
diff --git a/src/ol/renderer/dom/domimagelayerrenderer.js b/src/ol/renderer/dom/domimagelayerrenderer.js
index fabf03ea8c..0a8f59388b 100644
--- a/src/ol/renderer/dom/domimagelayerrenderer.js
+++ b/src/ol/renderer/dom/domimagelayerrenderer.js
@@ -107,7 +107,7 @@ ol.renderer.dom.ImageLayer.prototype.prepareFrame =
       !ol.extent.isEmpty(renderedExtent)) {
     var projection = viewState.projection;
     var sourceProjection = imageSource.getProjection();
-    if (goog.isDefAndNotNull(sourceProjection)) {
+    if (!goog.isNull(sourceProjection)) {
       goog.asserts.assert(ol.proj.equivalent(projection, sourceProjection));
       projection = sourceProjection;
     }
diff --git a/src/ol/renderer/webgl/webglimagelayerrenderer.js b/src/ol/renderer/webgl/webglimagelayerrenderer.js
index 07721bcb10..b8ce5a1fa0 100644
--- a/src/ol/renderer/webgl/webglimagelayerrenderer.js
+++ b/src/ol/renderer/webgl/webglimagelayerrenderer.js
@@ -127,7 +127,7 @@ ol.renderer.webgl.ImageLayer.prototype.prepareFrame =
       !ol.extent.isEmpty(renderedExtent)) {
     var projection = viewState.projection;
     var sourceProjection = imageSource.getProjection();
-    if (goog.isDefAndNotNull(sourceProjection)) {
+    if (!goog.isNull(sourceProjection)) {
       goog.asserts.assert(ol.proj.equivalent(projection, sourceProjection));
       projection = sourceProjection;
     }