diff --git a/src/finn/transformation/fpgadataflow/convert_to_hls_layers.py b/src/finn/transformation/fpgadataflow/convert_to_hls_layers.py
index 7b929edc4e672199a2eb6d7c8f427365af0dd9f5..e6dca0e4b05f943c971bc0f97af03f5038fd0dab 100644
--- a/src/finn/transformation/fpgadataflow/convert_to_hls_layers.py
+++ b/src/finn/transformation/fpgadataflow/convert_to_hls_layers.py
@@ -29,6 +29,7 @@
 
 from onnx import helper, TensorProto
 import numpy as np
+import warnings
 
 from finn.core.datatype import DataType
 from finn.transformation import Transformation