diff --git a/utshell-0.5/Cargo.toml b/utshell-0.5/Cargo.toml
index 49c15672e95367b0a239748baacd2e3f90ad8d82..22fa0e8a5eaecb1b5c87a7c432c206b010a050b0 100644
--- a/utshell-0.5/Cargo.toml
+++ b/utshell-0.5/Cargo.toml
@@ -97,7 +97,7 @@ members=[
  "r_bracecomp",
  "r_variables",
  "r_arrayfunc"
-]
+, "r_error"]
 
 [dependencies]
  libc = "*"
@@ -173,5 +173,6 @@ members=[
  r_array = {path = "./r_array"}
  r_bracecomp = {path = "./r_bracecomp"}
  r_variables = {path = "./r_variables"}
+ r_error = {path = "./r_error"}
 intl_pluralrules = "7.0.2"
 tinystr = "=0.7.1"
diff --git a/utshell-0.5/r_error/Cargo.toml b/utshell-0.5/r_error/Cargo.toml
new file mode 100644
index 0000000000000000000000000000000000000000..f2532fe16550b7b7bfa5ec6c5ca25d01f1d78ffe
--- /dev/null
+++ b/utshell-0.5/r_error/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "r_error"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/utshell-0.5/r_error/src/lib.rs b/utshell-0.5/r_error/src/lib.rs
new file mode 100644
index 0000000000000000000000000000000000000000..7d12d9af8195bf5e19d10c7b592b359ccd014149
--- /dev/null
+++ b/utshell-0.5/r_error/src/lib.rs
@@ -0,0 +1,14 @@
+pub fn add(left: usize, right: usize) -> usize {
+    left + right
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = add(2, 2);
+        assert_eq!(result, 4);
+    }
+}