diff --git a/src/rustup-cli/setup_mode.rs b/src/rustup-cli/setup_mode.rs
index 26191f257c..b822b684e6 100644
--- a/src/rustup-cli/setup_mode.rs
+++ b/src/rustup-cli/setup_mode.rs
@@ -1,10 +1,49 @@
 use std::env;
+use std::process;
 use self_update::{self, InstallOpts};
 use errors::*;
 use clap::{App, Arg, AppSettings};
 use rustup_dist::dist::TargetTriple;
 use common;
 
+mod sys_check {
+    #[cfg(unix)]
+    pub fn home_mismatch() -> bool {
+	extern crate libc as c;
+
+	use std::env;
+	use std::ffi::CStr;
+	use std::mem;
+	use std::ops::Deref;
+	use std::ptr;
+
+	// test runner should set this, nothing else
+	if env::var("RUSTUP_INIT_SKIP_SUDO_CHECK").as_ref().map(Deref::deref).ok() == Some("yes") {
+	    return false;
+	}
+	let mut pwd = unsafe { mem::uninitialized::<c::passwd>() };
+	let mut pwdp: *mut c::passwd = ptr::null_mut();
+	let mut buf = [0u8; 1024];
+	let rv = unsafe { c::getpwuid_r(c::geteuid(), &mut pwd, mem::transmute(&mut buf), buf.len(), &mut pwdp) };
+	if rv != 0 || pwdp == ptr::null_mut() {
+	    warn!("getpwuid_r: couldn't get user data");
+	    return false;
+	}
+	let pw_dir = unsafe { CStr::from_ptr(pwd.pw_dir) }.to_str().ok();
+	let env_home = env::var_os("HOME");
+	let env_home = env_home.as_ref().map(Deref::deref);
+	match (env_home, pw_dir) {
+	    (None, _) | (_, None) => false,
+	    (Some(ref eh), Some(ref pd)) => eh != pd
+	}
+    }
+
+    #[cfg(not(unix))]
+    pub fn home_mismatch() -> bool {
+	false
+    }
+}
+
 pub fn main() -> Result<()> {
     let args: Vec<_> = env::args().collect();
     let arg1 = args.get(1).map(|a| &**a);
@@ -39,6 +78,17 @@ pub fn main() -> Result<()> {
 
     let matches = cli.get_matches();
     let no_prompt = matches.is_present("no-prompt");
+    match (self::sys_check::home_mismatch(), no_prompt) {
+	(false, _) => (),
+	(true, false) => {
+	    err!("$HOME differs from euid-obtained home directory: you may be using sudo");
+	    err!("if this is what you want, restart the installation with `-y'");
+	    process::exit(1);
+	},
+	(true, true) => {
+	    warn!("$HOME differs from euid-obtained home directory: you may be using sudo");
+	}
+    }
     let verbose = matches.is_present("verbose");
     let default_host = matches.value_of("default-host").map(|s| s.to_owned()).unwrap_or_else(|| {
         TargetTriple::from_host_or_build().to_string()
diff --git a/src/rustup-mock/src/clitools.rs b/src/rustup-mock/src/clitools.rs
index 83ff319d2a..3074db01dd 100644
--- a/src/rustup-mock/src/clitools.rs
+++ b/src/rustup-mock/src/clitools.rs
@@ -242,6 +242,9 @@ pub fn env(config: &Config, cmd: &mut Command) {
     // This is only used for some installation tests on unix where CARGO_HOME
     // above is unset
     cmd.env("HOME", config.homedir.to_string_lossy().to_string());
+
+    // Setting HOME will confuse the sudo check for rustup-init. Override it
+    cmd.env("RUSTUP_INIT_SKIP_SUDO_CHECK", "yes");
 }
 
 pub fn run(config: &Config, name: &str, args: &[&str], env: &[(&str, &str)]) -> SanitizedOutput {