--- a/taskcluster/taskgraph/transforms/job/toolchain.py
+++ b/taskcluster/taskgraph/transforms/job/toolchain.py
@@ -4,16 +4,18 @@
 """
 Support for running toolchain-building jobs via dedicated scripts
 """
 
 from __future__ import absolute_import, print_function, unicode_literals
 
 import hashlib
 
+from mozbuild.shellutil import quote as shell_quote
+
 from taskgraph.util.schema import Schema
 from voluptuous import Optional, Required, Any
 
 from taskgraph.transforms.job import run_job_using
 from taskgraph.transforms.job.common import (
     docker_worker_add_tc_vcs_cache,
     docker_worker_add_gecko_vcs_env_vars,
     docker_worker_add_public_artifacts,
@@ -29,16 +31,19 @@ TOOLCHAIN_INDEX = 'gecko.cache.level-{le
 toolchain_run_schema = Schema({
     Required('using'): 'toolchain-script',
 
     # The script (in taskcluster/scripts/misc) to run.
     # Python scripts are invoked with `mach python` so vendored libraries
     # are available.
     Required('script'): basestring,
 
+    # Arguments to pass to the script.
+    Optional('arguments'): [basestring],
+
     # If not false, tooltool downloads will be enabled via relengAPIProxy
     # for either just public files, or all files.  Not supported on Windows
     Required('tooltool-downloads', default=False): Any(
         False,
         'public',
         'internal',
     ),
 
@@ -61,31 +66,36 @@ def add_optimization(config, run, taskde
     files.append('taskcluster/taskgraph/transforms/job/toolchain.py')
     # The script
     files.append('taskcluster/scripts/misc/{}'.format(run['script']))
     # Tooltool manifest if any is defined:
     tooltool_manifest = taskdesc['worker']['env'].get('TOOLTOOL_MANIFEST')
     if tooltool_manifest:
         files.append(tooltool_manifest)
 
-    digest = hash_paths(GECKO, files)
+    # Accumulate dependency hashes for index generation.
+    data = [hash_paths(GECKO, files)]
 
     # If the task has dependencies, we need those dependencies to influence
     # the index path. So take the digest from the files above, add the list
     # of its dependencies, and hash the aggregate.
     # If the task has no dependencies, just use the digest from above.
     deps = taskdesc['dependencies']
     if deps:
-        data = [digest] + sorted(deps.values())
-        digest = hashlib.sha256('\n'.join(data)).hexdigest()
+        data.extend(sorted(deps.values()))
+
+    # Likewise script arguments should influence the index.
+    args = run.get('arguments')
+    if args:
+        data.extend(args)
 
     label = taskdesc['label']
     subs = {
         'name': label.replace('%s-' % config.kind, ''),
-        'digest': digest,
+        'digest': hashlib.sha256('\n'.join(data)).hexdigest()
     }
 
     # We'll try to find a cached version of the toolchain at levels above
     # and including the current level, starting at the highest level.
     index_routes = []
     for level in reversed(range(int(config.params['level']), 4)):
         subs['level'] = level
         index_routes.append(TOOLCHAIN_INDEX.format(**subs))
@@ -123,26 +133,30 @@ def docker_worker_toolchain(config, job,
         docker_worker_add_tooltool(config, job, taskdesc, internal=internal)
 
     # Use `mach` to invoke python scripts so in-tree libraries are available.
     if run['script'].endswith('.py'):
         wrapper = 'workspace/build/src/mach python '
     else:
         wrapper = ''
 
+    args = run.get('arguments', '')
+    if args:
+        args = ' ' + shell_quote(*args)
+
     worker['command'] = [
         '/builds/worker/bin/run-task',
         '--vcs-checkout=/builds/worker/workspace/build/src',
         '--sparse-profile', 'build/sparse-profiles/toolchain-build',
         '--',
         'bash',
         '-c',
         'cd /builds/worker && '
-        '{}workspace/build/src/taskcluster/scripts/misc/{}'.format(
-            wrapper, run['script'])
+        '{}workspace/build/src/taskcluster/scripts/misc/{}{}'.format(
+            wrapper, run['script'], args)
     ]
 
     attributes = taskdesc.setdefault('attributes', {})
     attributes['toolchain-artifact'] = run['toolchain-artifact']
     if 'toolchain-alias' in run:
         attributes['toolchain-alias'] = run['toolchain-alias']
 
     add_optimization(config, run, taskdesc)
@@ -179,21 +193,26 @@ def windows_toolchain(config, job, taskd
     hg_command.extend(['--revision', '%GECKO_HEAD_REV%'])
     hg_command.append('%GECKO_HEAD_REPOSITORY%')
     hg_command.append('.\\build\\src')
 
     # Use `mach` to invoke python scripts so in-tree libraries are available.
     if run['script'].endswith('.py'):
         raise NotImplementedError("Python scripts don't work on Windows")
 
+    args = run.get('arguments', '')
+    if args:
+        args = ' ' + shell_quote(*args)
+
     bash = r'c:\mozilla-build\msys\bin\bash'
     worker['command'] = [
         ' '.join(hg_command),
         # do something intelligent.
-        r'{} -c ./build/src/taskcluster/scripts/misc/{}'.format(bash, run['script'])
+        r'{} build/src/taskcluster/scripts/misc/{}{}'.format(
+            bash, run['script'], args)
     ]
 
     attributes = taskdesc.setdefault('attributes', {})
     attributes['toolchain-artifact'] = run['toolchain-artifact']
     if 'toolchain-alias' in run:
         attributes['toolchain-alias'] = run['toolchain-alias']
 
     add_optimization(config, run, taskdesc)