diff --git a/src/env/env.rs b/src/env/env.rs
index 0203e3ba8..931277bb6 100644
--- a/src/env/env.rs
+++ b/src/env/env.rs
@@ -47,7 +47,7 @@ pub fn uumain(args: Vec<String>) -> i32 {
         .optflag(
             "0",
             "null",
-            "end each output line with a 0 byte rather than newline",
+            "end each output line with a 0 byte rather than newline (only valid when printing the environment)",
         )
         .optopt("u", "unset", "remove variable from the environment", "NAME");
 
@@ -103,14 +103,14 @@ pub fn uumain(args: Vec<String>) -> i32 {
                     let var = iter.next();
 
                     match var {
-                        None => println!("{}: this option requires an argument: {}", NAME, opt),
+                        None => eprintln!("{}: this option requires an argument: {}", NAME, opt),
                         Some(s) => opts.unsets.push(s.to_owned()),
                     }
                 }
 
                 _ => {
-                    println!("{}: invalid option \"{}\"", NAME, *opt);
-                    println!("Type \"{} --help\" for detailed informations", NAME);
+                    eprintln!("{}: invalid option \"{}\"", NAME, *opt);
+                    eprintln!("Type \"{} --help\" for detailed information", NAME);
                     return 1;
                 }
             }
@@ -134,13 +134,13 @@ pub fn uumain(args: Vec<String>) -> i32 {
                         let var = iter.next();
 
                         match var {
-                            None => println!("{}: this option requires an argument: {}", NAME, opt),
+                            None => eprintln!("{}: this option requires an argument: {}", NAME, opt),
                             Some(s) => opts.unsets.push(s.to_owned()),
                         }
                     }
                     _ => {
-                        println!("{}: illegal option -- {}", NAME, c);
-                        println!("Type \"{} --help\" for detailed informations", NAME);
+                        eprintln!("{}: illegal option -- {}", NAME, c);
+                        eprintln!("Type \"{} --help\" for detailed information", NAME);
                         return 1;
                     }
                 }
@@ -159,6 +159,11 @@ pub fn uumain(args: Vec<String>) -> i32 {
                 }
                 // no, its a program-like opt
                 _ => {
+                    if opts.null {
+                        eprintln!("{}: cannot specify --null (-0) with command", NAME);
+                        eprintln!("Type \"{} --help\" for detailed information", NAME);
+                        return 1;
+                    }
                     opts.program.push(opt.clone());
                     break;
                 }
@@ -170,6 +175,11 @@ pub fn uumain(args: Vec<String>) -> i32 {
 
     // read program arguments
     for opt in iter {
+        if opts.null {
+            eprintln!("{}: cannot specify --null (-0) with command", NAME);
+            eprintln!("Type \"{} --help\" for detailed information", NAME);
+            return 1;
+        }
         opts.program.push(opt.clone())
     }
 
diff --git a/tests/common/util.rs b/tests/common/util.rs
index 43fe255f7..38b92fa24 100755
--- a/tests/common/util.rs
+++ b/tests/common/util.rs
@@ -606,7 +606,7 @@ impl UCommand {
     }
 
     /// Spawns the command, feeds the stdin if any, waits for the result,
-    /// asserts success, and returns a command result.
+    /// asserts failure, and returns a command result.
     pub fn fails(&mut self) -> CmdResult {
         let cmd_result = self.run();
         cmd_result.failure();
diff --git a/tests/test_env.rs b/tests/test_env.rs
index 6646d5af7..6b81d1e48 100644
--- a/tests/test_env.rs
+++ b/tests/test_env.rs
@@ -81,3 +81,9 @@ fn test_unset_variable() {
 
     assert_eq!(out.lines().any(|line| line.starts_with("HOME=")), false);
 }
+
+#[test]
+fn test_fail_null_with_program() {
+    let out = new_ucmd!().arg("--null").arg("cd").fails().stderr;
+    assert!(out.contains("cannot specify --null (-0) with command"));
+}