Forgot applying it to BinaryLoader too.

src/extras/loaders/BinaryLoader.js

@@ -92,7 +92,7 @@ THREE.BinaryLoader.prototype.loadAjaxJSON = function( context, url, callback, te
 	};
 
 	xhr.open( "GET", url, true );
-	xhr.overrideMimeType( "text/plain; charset=x-user-defined" );
+	if ( xhr.overrideMimeType ) xhr.overrideMimeType( "text/plain; charset=x-user-defined" );
 	xhr.setRequestHeader( "Content-Type", "text/plain" );
 	xhr.send( null );