diff --git a/src/lib.rs b/src/lib.rs
index 026c945..0f1dd11 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -667,7 +667,10 @@ impl Shell {
     ///
     /// The returned hash map contains a snapshot of the process’s environment variables at the time of this invocation. Modifications to environment variables afterwards will not be reflected in the returned iterator.
     pub fn vars_os(&self) -> Vec<(OsString, OsString)> {
-        Vec::from_iter(self.env.borrow().iter().map(|(k, v)| (k.to_owned(), v.to_owned())))
+        let mut vars =
+            Vec::from_iter(self.env.borrow().iter().map(|(k, v)| (k.to_owned(), v.to_owned())));
+        vars.sort_unstable_by(|(a, _), (b, _)| a.cmp(b));
+        vars
     }
 
     /// Returns the environment variables set for this shell.
@@ -682,12 +685,14 @@ impl Shell {
     /// the environment is not valid unicode. If this is not desired, consider
     /// using [`Shell::vars_os`](Self::vars_os).
     pub fn vars(&self) -> Vec<(String, String)> {
-        Vec::from_iter(
+        let mut vars = Vec::from_iter(
             self.env
                 .borrow()
                 .iter()
                 .map(|(k, v)| (k.to_str().unwrap().to_string(), v.to_str().unwrap().to_string())),
-        )
+        );
+        vars.sort_unstable_by(|(a, _), (b, _)| a.cmp(b));
+        vars
     }
 }