diff --git a/lcnn/models/line_vectorizer.py b/lcnn/models/line_vectorizer.py
index ecbfbfb..2a77f26 100644
--- a/lcnn/models/line_vectorizer.py
+++ b/lcnn/models/line_vectorizer.py
@@ -194,7 +194,7 @@ def sample_lines(self, meta, jmap, joff, do_evaluation):
             if do_evaluation:
                 c = (u < v).flatten()
             else:
-                c = torch.zeros_like(label)
+                c = torch.zeros_like(label, dtype=torch.bool)
 
                 # sample positive lines
                 cdx = label.nonzero().flatten()