diff --git a/.github/workflows/lexer.yml b/.github/workflows/lexer.yml
index 9d737ee..b760099 100644
--- a/.github/workflows/lexer.yml
+++ b/.github/workflows/lexer.yml
@@ -53,3 +53,4 @@ jobs:
         if: steps.changed-lexer.outputs.files_changed == 'true'
         run: |
           echo "::error title=Lexer not up-to-date::Generated src/lexer.jl has uncommitted changes."
+          exit 1