diff --git a/pyzx/optimize.py b/pyzx/optimize.py
index f047111c..44c36acd 100644
--- a/pyzx/optimize.py
+++ b/pyzx/optimize.py
@@ -512,9 +512,9 @@ def parse_gate(self, g: Gate) -> None:
             else: # Only the control has a hadamard gate in front of it
                 self.add_hadamard(c)
                 self.add_cnot(g)
-        
+
         else:
-            raise TypeError("Unknown gate {}".format(str(g)))
+            raise TypeError("Unknown gate {}. Maybe simplify the gates with circuit.to_basic_gates()?".format(str(g)))