diff --git a/robosat/unet.py b/robosat/unet.py
index e9e4c5b3..bedabea1 100644
--- a/robosat/unet.py
+++ b/robosat/unet.py
@@ -116,6 +116,8 @@ def forward(self, x):
         Returns:
           The networks output tensor.
         """
+        size = x.size()
+        assert size[-1] % 32 == 0 and size[-2] % 32 == 0, "image resolution has to be divisible by 32 for resnet"
 
         enc0 = self.resnet.conv1(x)
         enc0 = self.resnet.bn1(enc0)