diff --git a/src/uu/dircolors/src/dircolors.rs b/src/uu/dircolors/src/dircolors.rs
index 2bf8b517e44..39edca87611 100644
--- a/src/uu/dircolors/src/dircolors.rs
+++ b/src/uu/dircolors/src/dircolors.rs
@@ -37,9 +37,9 @@ pub enum OutputFmt {
     Unknown,
 }
 
-pub fn guess_syntax() -> OutputFmt {
-    match env::var("SHELL") {
-        Ok(ref s) if !s.is_empty() => {
+pub fn guess_syntax(env: Option<OsString>) -> OutputFmt {
+    match env {
+        Some(s) if !s.is_empty() => {
             let shell_path: &Path = s.as_ref();
             if let Some(name) = shell_path.file_name() {
                 if name == "csh" || name == "tcsh" {
@@ -165,7 +165,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     };
 
     if out_format == OutputFmt::Unknown {
-        match guess_syntax() {
+        match guess_syntax(env::var_os("SHELL")) {
             OutputFmt::Unknown => {
                 return Err(USimpleError::new(
                     1,
diff --git a/tests/by-util/test_dircolors.rs b/tests/by-util/test_dircolors.rs
index dd98e5d43ce..e2eb774604f 100644
--- a/tests/by-util/test_dircolors.rs
+++ b/tests/by-util/test_dircolors.rs
@@ -32,46 +32,14 @@ fn test_invalid_arg() {
 
 #[test]
 fn test_shell_syntax() {
-    use std::env;
-    let last = env::var("SHELL");
-    unsafe {
-        env::set_var("SHELL", "/path/csh");
-    }
-    assert_eq!(OutputFmt::CShell, guess_syntax());
-    unsafe {
-        env::set_var("SHELL", "csh");
-    }
-    assert_eq!(OutputFmt::CShell, guess_syntax());
-    unsafe {
-        env::set_var("SHELL", "/path/bash");
-    }
-    assert_eq!(OutputFmt::Shell, guess_syntax());
-    unsafe {
-        env::set_var("SHELL", "bash");
-    }
-    assert_eq!(OutputFmt::Shell, guess_syntax());
-    unsafe {
-        env::set_var("SHELL", "/asd/bar");
-    }
-    assert_eq!(OutputFmt::Shell, guess_syntax());
-    unsafe {
-        env::set_var("SHELL", "foo");
-    }
-    assert_eq!(OutputFmt::Shell, guess_syntax());
-    unsafe {
-        env::set_var("SHELL", "");
-    }
-    assert_eq!(OutputFmt::Unknown, guess_syntax());
-    unsafe {
-        env::remove_var("SHELL");
-    }
-    assert_eq!(OutputFmt::Unknown, guess_syntax());
-
-    if let Ok(s) = last {
-        unsafe {
-            env::set_var("SHELL", s);
-        }
-    }
+    assert_eq!(OutputFmt::CShell, guess_syntax(Some("/path/csh".into())));
+    assert_eq!(OutputFmt::CShell, guess_syntax(Some("csh".into())));
+    assert_eq!(OutputFmt::Shell, guess_syntax(Some("/path/bash".into())));
+    assert_eq!(OutputFmt::Shell, guess_syntax(Some("bash".into())));
+    assert_eq!(OutputFmt::Shell, guess_syntax(Some("/asd/bar".into())));
+    assert_eq!(OutputFmt::Shell, guess_syntax(Some("foo".into())));
+    assert_eq!(OutputFmt::Unknown, guess_syntax(Some(String::new().into())));
+    assert_eq!(OutputFmt::Unknown, guess_syntax(None));
 }
 
 #[test]