diff --git a/docs/source/code_examples/macro_commands/synth_ice40.ys b/docs/source/code_examples/macro_commands/synth_ice40.ys
index 443b8e0b0..07d960a64 100644
--- a/docs/source/code_examples/macro_commands/synth_ice40.ys
+++ b/docs/source/code_examples/macro_commands/synth_ice40.ys
@@ -6,6 +6,7 @@ begin:
     proc
 
 flatten:
+    check
     flatten
     tribuf -logic
     deminout