diff --git a/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-ui/src/main/java/org/deeplearning4j/ui/weights/ConvolutionalIterationListener.java b/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-ui/src/main/java/org/deeplearning4j/ui/weights/ConvolutionalIterationListener.java
index 037c44b40..4aae630ca 100644
--- a/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-ui/src/main/java/org/deeplearning4j/ui/weights/ConvolutionalIterationListener.java
+++ b/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-ui/src/main/java/org/deeplearning4j/ui/weights/ConvolutionalIterationListener.java
@@ -140,7 +140,7 @@ public class ConvolutionalIterationListener extends BaseTrainingListener {
                 ComputationGraph l = (ComputationGraph) model;
                 Layer[] layers = l.getLayers();
                 if(layers.length != activations.size())
-                    throw new RuntimeException();
+                    throw new RuntimeException("layers.length != activations.size(). Got layers.length="+layers.length+", activations.size()="+activations.size());
                 for( int i=0; i<layers.length; i++ ){
                     if(layers[i].type() == Layer.Type.CONVOLUTIONAL){
                         String layerName = layers[i].conf().getLayer().getLayerName();
diff --git a/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-vertx/src/main/java/org/deeplearning4j/ui/module/convolutional/ConvolutionalListenerModule.java b/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-vertx/src/main/java/org/deeplearning4j/ui/module/convolutional/ConvolutionalListenerModule.java
index 0df50032f..3236e9b2f 100644
--- a/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-vertx/src/main/java/org/deeplearning4j/ui/module/convolutional/ConvolutionalListenerModule.java
+++ b/deeplearning4j/deeplearning4j-ui-parent/deeplearning4j-vertx/src/main/java/org/deeplearning4j/ui/module/convolutional/ConvolutionalListenerModule.java
@@ -105,22 +105,22 @@ public class ConvolutionalListenerModule implements UIModule {
                 BufferedImage bi = clp.getImg();
                 ByteArrayOutputStream baos = new ByteArrayOutputStream();
                 try {
-                    ImageIO.write(bi, "jpg", baos);
+                    ImageIO.write(bi, "png", baos);
                 } catch (IOException e) {
                     log.warn("Error displaying image", e);
                 }
 
                 rc.response()
-                        .putHeader("content-type", "image/jpg")
+                        .putHeader("content-type", "image/png")
                         .end(Buffer.buffer(baos.toByteArray()));
             } else {
                 rc.response()
-                        .putHeader("content-type", "image/jpg")
+                        .putHeader("content-type", "image/png")
                         .end(Buffer.buffer(new byte[0]));
             }
         } else {
             rc.response()
-                    .putHeader("content-type", "image/jpg")
+                    .putHeader("content-type", "image/png")
                     .end(Buffer.buffer(new byte[0]));
         }
     }