--- a/python/mozboot/mozboot/base.py
+++ b/python/mozboot/mozboot/base.py
@@ -68,26 +68,43 @@ the $PATH environment variable.
 
 We recommend the following tools for installing Python:
 
     pyenv   -- https://github.com/yyuu/pyenv)
     pythonz -- https://github.com/saghul/pythonz
     official installers -- http://www.python.org/
 '''
 
-RUST_NOT_IN_PATH = '''
-You have some rust files in %(cargo_bin)s, but they're not part of the
-standard PATH.'''
+RUST_INSTALL_COMPLETE = '''
+Rust installation complete. You should now have rustc and cargo
+in %(cargo_bin)s
+
+The installer tries to add these to your default shell PATH, so
+restarting your shell and running this script again may work.
+If it doesn't, you'll need to add the new command location
+manually.
+
+If restarting doesn't work, edit your shell initialization
+script, which may be called ~/.bashrc or ~/.bash_profile or
+~/.profile, and add the following line:
 
-RUST_PATH_ADVICE = '''
-To make these available, please add this directory to the PATH variable
-in your shell initialization script, which may be called ~/.bashrc or
-~/.bash_profile or ~/.profile. Edit this and add the following line:
+    %(cmd)s
+
+Then restart your shell and run the bootstrap script again.
+'''
 
-    source %(cargo_home)s/env
+RUST_NOT_IN_PATH = '''
+You have some rust files in %(cargo_bin)s
+but they're not part of this shell's PATH.
+
+To add these to the PATH, edit your shell initialization
+script, which may be called ~/.bashrc or ~/.bash_profile or
+~/.profile, and add the following line:
+
+    %(cmd)s
 
 Then restart your shell and run the bootstrap script again.
 '''
 
 RUSTUP_OLD = '''
 We found an executable called `rustup` which we normally use to install
 and upgrade Rust programming language support, but we didn't understand
 its output. It may be an old version, or not be the installer from
@@ -103,18 +120,17 @@ We attempted to upgrade Rust to a modern
 However, you appear to still have version %s.
 
 It's possible rustup failed. It's also possible the new Rust is not being
 installed in the search path for this shell. Try creating a new shell and
 run this bootstrapper again.
 
 If this continues to fail and you are sure you have a modern Rust on your
 system, ensure it is on the $PATH and try again. If that fails, you'll need to
-install Rust manually and ensure the path with the rustc and cargo  binaries
-are listed in the $PATH environment variable.
+install Rust manually.
 
 We recommend the installer from https://rustup.rs/ for installing Rust,
 but you may be able to get a recent enough version from a software install
 tool or package manager on your system, or directly from https://rust-lang.org/
 '''
 
 BROWSER_ARTIFACT_MODE_MOZCONFIG = '''
 Paste the lines between the chevrons (>>> and <<<) into your mozconfig file:
@@ -516,36 +532,51 @@ class BaseBootstrapper(object):
         return our >= MODERN_RUST_VERSION, our
 
     def cargo_home(self):
         cargo_home = os.environ.get('CARGO_HOME',
                 os.path.expanduser(os.path.join('~', '.cargo')))
         cargo_bin = os.path.join(cargo_home, 'bin')
         return cargo_home, cargo_bin
 
+    def print_rust_path_advice(self, template, cargo_home, cargo_bin):
+        # Suggest ~/.cargo/env if it exists.
+        if os.path.exists(os.path.join(cargo_home, 'env')):
+            cmd = 'source %s/env' % cargo_home
+        else:
+            # On Windows rustup doesn't write out ~/.cargo/env
+            # so fall back to a manual PATH update. Bootstrap
+            # only runs under msys, so a unix-style shell command
+            # is appropriate there.
+            cmd = 'export PATH=%s:$PATH' % cargo_bin
+        print(template % {
+            'cargo_bin': cargo_bin,
+            'cmd': cmd,
+        })
+
     def ensure_rust_modern(self):
         modern, version = self.is_rust_modern()
 
         if modern:
             print('Your version of Rust (%s) is new enough.' % version)
             return
 
         if not version:
             # Rust wasn't in PATH. Check the standard location.
             cargo_home, cargo_bin = self.cargo_home()
             try_rustc = os.path.join(cargo_bin, 'rustc' + rust.exe_suffix())
             try_cargo = os.path.join(cargo_bin, 'cargo' + rust.exe_suffix())
             have_rustc = os.path.exists(try_rustc)
             have_cargo = os.path.exists(try_cargo)
             if have_rustc or have_cargo:
-                print(RUST_NOT_IN_PATH % { 'cargo_bin': cargo_bin })
-                print(RUST_PATH_ADVICE % { 'cargo_home': cargo_home })
+                self.print_rust_path_advice(RUST_NOT_IN_PATH,
+                        cargo_home, cargo_bin)
                 sys.exit(1)
-
-        print('Your version of Rust (%s) is too old.' % version)
+        else:
+            print('Your version of Rust (%s) is too old.' % version)
 
         rustup = self.which('rustup')
         if rustup:
             rustup_version = self._parse_version(rustup)
             if not rustup_version:
                 print(RUSTUP_OLD)
                 sys.exit(1)
             print('Found rustup. Will try to upgrade.')
@@ -586,19 +617,18 @@ class BaseBootstrapper(object):
             os.chmod(rustup_init, mode | stat.S_IRWXU)
             print('Ok')
             print('Running rustup-init...')
             subprocess.check_call([rustup_init, '-y',
                 '--default-toolchain', 'stable',
                 '--default-host', platform,
             ])
             cargo_home, cargo_bin = self.cargo_home()
-            print('Rust installation complete.')
-            print('You should now have rustc and cargo in %s' % cargo_bin)
-            print(RUST_PATH_ADVICE % { 'cargo_home': cargo_home })
+            self.print_rust_path_advice(RUST_INSTALL_COMPLETE,
+                    cargo_home, cargo_bin)
         finally:
             try:
                 os.remove(rustup_init)
             except OSError as e:
                 if e.errno != errno.ENOENT:
                     raise
 
     def http_download_and_save(self, url, dest, sha256hexhash):