diff --git a/recurrentshop/engine.py b/recurrentshop/engine.py
index 2109516..af62acd 100644
--- a/recurrentshop/engine.py
+++ b/recurrentshop/engine.py
@@ -4,6 +4,7 @@
 from .backend import rnn, learning_phase_scope
 from .generic_utils import serialize_function, deserialize_function
 from keras.engine.base_layer import Node,_collect_previous_mask, _collect_input_shape
+from keras import backend as K
 import inspect