diff --git a/src/renderers/WebGLRenderer.js b/src/renderers/WebGLRenderer.js
index e2496f7c75e31642ed1b0c8a8ba994ee01478841..dc66729ddf4223a0099e4319e8e79b747f2e43c6 100644
--- a/src/renderers/WebGLRenderer.js
+++ b/src/renderers/WebGLRenderer.js
@@ -1244,7 +1244,7 @@ THREE.WebGLRenderer = function ( parameters ) {
 
 			var type, size;
 
-			if ( index.array instanceof Uint32Array ) {
+			if ( index.array instanceof Uint32Array && extensions.get( 'OES_element_index_uint' ) ) {
 
 				type = _gl.UNSIGNED_INT;
 				size = 4;