diff --git a/keras_retinanet/backend/tensorflow_backend.py b/keras_retinanet/backend/tensorflow_backend.py
index 7de5b2ea9..a0969feea 100644
--- a/keras_retinanet/backend/tensorflow_backend.py
+++ b/keras_retinanet/backend/tensorflow_backend.py
@@ -68,16 +68,10 @@ def resize_images(images, size, method='bilinear', align_corners=False):
     return tensorflow.image.resize_images(images, size, methods[method], align_corners)
 
 
-def non_max_suppression(boxes, scores, max_output_size, iou_threshold, **kwargs):
+def non_max_suppression(*args, **kwargs):
     """ See https://www.tensorflow.org/versions/master/api_docs/python/tf/image/non_max_suppression .
     """
-    return tensorflow.image.non_max_suppression(
-            boxes=tensorflow.cast(boxes, tensorflow.float32),
-            scores=tensorflow.cast(scores, tensorflow.float32),
-            max_output_size=max_output_size,
-            iou_threshold=iou_threshold,
-            **kwargs
-        )
+    return tensorflow.image.non_max_suppression(*args, **kwargs)
 
 
 def range(*args, **kwargs):
diff --git a/keras_retinanet/layers/filter_detections.py b/keras_retinanet/layers/filter_detections.py
index 210cce43d..f73e918b2 100644
--- a/keras_retinanet/layers/filter_detections.py
+++ b/keras_retinanet/layers/filter_detections.py
@@ -57,7 +57,7 @@ def _filter_detections(scores, labels):
             filtered_scores = keras.backend.gather(scores, indices)[:, 0]
 
             # perform NMS
-            nms_indices = backend.non_max_suppression(boxes=filtered_boxes, scores=filtered_scores, max_output_size=max_detections, iou_threshold=nms_threshold)
+            nms_indices = backend.non_max_suppression(filtered_boxes, filtered_scores, max_output_size=max_detections, iou_threshold=nms_threshold)
 
             # filter indices based on NMS
             indices = keras.backend.gather(indices, nms_indices)
diff --git a/keras_retinanet/utils/image.py b/keras_retinanet/utils/image.py
index 6be9cd7ee..b372cf493 100644
--- a/keras_retinanet/utils/image.py
+++ b/keras_retinanet/utils/image.py
@@ -49,7 +49,7 @@ def preprocess_image(x, mode='caffe'):
     # mostly identical to "https://github.com/keras-team/keras-applications/blob/master/keras_applications/imagenet_utils.py"
     # except for converting RGB -> BGR since we assume BGR already
 
-    #covert always to float32 to keep compatibility with opencv
+    # covert always to float32 to keep compatibility with opencv
     x = x.astype(np.float32)
 
     if mode == 'tf':
@@ -62,6 +62,7 @@ def preprocess_image(x, mode='caffe'):
 
     return x
 
+
 def cast_image_to_floatx(x):
     """ Convert an image to the actual keras floatx.
 
@@ -75,6 +76,7 @@ def cast_image_to_floatx(x):
 
     return x
 
+
 def adjust_transform_for_image(transform, image, relative_translation):
     """ Adjust a transformation for a specific image.