diff --git a/run_electrum b/run_electrum
index 8e998465..ebb29ca9 100755
--- a/run_electrum
+++ b/run_electrum
@@ -397,9 +397,8 @@ if __name__ == '__main__':
         constants.set_regtest()
     elif config.get('simnet'):
         constants.set_simnet()
-
-    if config.get('simnet'):
-        constants.set_simnet()
+    else:
+        raise Exception('lightning branch not available on mainnet')
 
     # run non-RPC commands separately
     if cmdname in ['create', 'restore']: