--- a/python/mozboot/mozboot/base.py
+++ b/python/mozboot/mozboot/base.py
@@ -377,16 +377,18 @@ class BaseBootstrapper(object):
         different from the basename of the executable.
 
         An optional env argument allows modifying environment
         variable during the invocation to set options, PATH,
         etc.
         '''
         if not name:
             name = os.path.basename(path)
+        if name.endswith('.exe'):
+            name = name[:-4]
 
         info = self.check_output([path, '--version'],
                                  env=env,
                                  stderr=subprocess.STDOUT)
         match = re.search(name + ' ([a-z0-9\.]+)', info)
         if not match:
             print('ERROR! Unable to identify %s version.' % name)
             return None
@@ -501,17 +503,17 @@ class BaseBootstrapper(object):
     def is_rust_modern(self):
         rustc = self.which('rustc')
         if not rustc:
             print('Could not find a Rust compiler.')
             return False, None
 
         cargo = self.which('cargo')
 
-        our = self._parse_version(rust)
+        our = self._parse_version(rustc)
         if not our:
             return False, None
 
         return our >= MODERN_RUST_VERSION, our
 
     def ensure_rust_modern(self):
         modern, version = self.is_rust_modern()
 
@@ -519,18 +521,20 @@ class BaseBootstrapper(object):
             print('Your version of Rust (%s) is new enough.' % version)
             return
 
         if not version:
             # Rust wasn't in PATH. Try the standard path.
             cargo_home = os.environ.get('CARGO_HOME',
                     os.path.expanduser(os.path.join('~', '.cargo')))
             cargo_bin = os.path.join(cargo_home, 'bin')
-            have_rustc = os.path.exists(os.path.join(cargo_bin, 'rustc'))
-            have_cargo = os.path.exists(os.path.join(cargo_bin, 'cargo'))
+            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,
                                            'cargo_home': cargo_home })
                 sys.exit(1)
 
         rustup = self.which('rustup')
         if rustup:
             rustup_version = self._parse_version(rustup)

--- a/python/mozboot/mozboot/rust.py
+++ b/python/mozboot/mozboot/rust.py
@@ -36,24 +36,21 @@ NO_PLATFORM = '''
 Sorry, we have no installer configured for your platform.
 
 Please try installing rust for your system from https://rustup.rs/
 or from https://rust-lang.org/ or from your package manager.
 '''
 
 def rustup_url(host, version=RUSTUP_VERSION):
     '''Download url for a particular version of the installer.'''
-    ext = ''
-    if 'windows' in host:
-        ext = '.exe'
-    return os.path.join(RUSTUP_URL_BASE,
-        'archive/%(version)s/%(host)s/rustup-init%(ext)s') % {
+    return '%(base)s/archive/%(version)s/%(host)s/rustup-init%(ext)s' % {
+                'base': RUSTUP_URL_BASE,
                 'version': version,
                 'host': host,
-                'ext': ext}
+                'ext': exe_suffix(host)}
 
 def rustup_hash(host):
     '''Look up the checksum for the given installer.'''
     return RUSTUP_HASHES.get(host, None)
 
 def platform():
     '''Determine the appropriate rust platform string for the current host'''
     if sys.platform.startswith('darwin'):
@@ -63,16 +60,23 @@ def platform():
         return 'x86_64-pc-windows-msvc'
     elif sys.platform.startswith('linux'):
         return 'x86_64-unknown-linux-gnu'
     elif sys.platform.startswith('freebsd'):
         return 'x86_64-unknown-freebsd'
 
     return None
 
+def exe_suffix(host=None):
+    if not host:
+        host = platform()
+    if 'windows' in host:
+        return '.exe'
+    return ''
+
 USAGE = '''
 python rust.py [--update]
 
 Pass the --update option print info for the latest release of rustup-init.
 
 When invoked without the --update option, it queries the latest version
 and verifies the current stored checksums against the distribution server,
 but doesn't update the version installed by `mach bootstrap`.