diff --git a/io/signal.py b/io/signal.py
index 158cc976384cde9efab4ce2981e667666872464f..b486737d6a33961bd0e5007119c025ce4ab05941 100644
--- a/io/signal.py
+++ b/io/signal.py
@@ -138,7 +138,7 @@ class Signal(BridgeH5):
                     else:
                         index = pd.Index([], name=merged.index.name)
                     merged = pd.DataFrame([], index=index)
-            return merged
+        return merged
 
     @property
     def datasets(self):