diff --git a/buildpacks/ruby/src/steps/get_default_process.rs b/buildpacks/ruby/src/steps/get_default_process.rs
index 8683411c..d2bf670e 100644
--- a/buildpacks/ruby/src/steps/get_default_process.rs
+++ b/buildpacks/ruby/src/steps/get_default_process.rs
@@ -90,6 +90,7 @@ fn default_rails() -> Process {
         .args([
             "-c",
             &[
+                "set -eu;",
                 "bin/rails server",
                 "--port \"$PORT\"",
                 "--environment \"$RAILS_ENV\"",