diff --git a/scripts/build-downstream-projects.sh b/scripts/build-downstream-projects.sh
index fe480c93e..7fb2f5378 100755
--- a/scripts/build-downstream-projects.sh
+++ b/scripts/build-downstream-projects.sh
@@ -83,6 +83,7 @@ serum_dex() {
     rm -rf serum-dex
     git clone https://github.com/project-serum/serum-dex.git  # TODO: Consider using a tag
     cd serum-dex
+    git checkout 991a86e93c22667b6b0fbb01914395d332be5531 # Known good commit: https://github.com/project-serum/serum-dex/commit/991a86e93c22667b6b0fbb01914395d332be5531
 
     update_solana_dependencies .
     patch_crates_io Cargo.toml