--- a/taskcluster/taskgraph/transforms/repackage.py
+++ b/taskcluster/taskgraph/transforms/repackage.py
@@ -218,17 +218,17 @@ def make_job_description(config, jobs):
             attributes['locale'] = locale
 
         treeherder = job.get('treeherder', {})
         if attributes.get('nightly'):
             treeherder.setdefault('symbol', 'Nr')
         else:
             treeherder.setdefault('symbol', 'Rpk')
         dep_th_platform = dep_job.task.get('extra', {}).get('treeherder-platform')
-        treeherder.setdefault('platform', "{}/opt".format(dep_th_platform))
+        treeherder.setdefault('platform', dep_th_platform)
         treeherder.setdefault('tier', 1)
         treeherder.setdefault('kind', 'build')
 
         if config.kind == 'repackage-msi':
             treeherder['symbol'] = 'MSI({})'.format(locale or 'N')
 
         build_task = None
         signing_task = None

--- a/taskcluster/taskgraph/transforms/repackage_signing.py
+++ b/taskcluster/taskgraph/transforms/repackage_signing.py
@@ -47,18 +47,17 @@ def make_repackage_signing_description(c
         attributes['repackage_type'] = 'repackage-signing'
 
         treeherder = job.get('treeherder', {})
         if attributes.get('nightly'):
             treeherder.setdefault('symbol', 'rs(N)')
         else:
             treeherder.setdefault('symbol', 'rs(B)')
         dep_th_platform = dep_job.task.get('extra', {}).get('treeherder-platform')
-        treeherder.setdefault('platform',
-                              "{}/opt".format(dep_th_platform))
+        treeherder.setdefault('platform', dep_th_platform)
         treeherder.setdefault(
             'tier',
             dep_job.task.get('extra', {}).get('treeherder', {}).get('tier', 1)
             )
         treeherder.setdefault('kind', 'build')
 
         if locale:
             treeherder['symbol'] = 'rs({})'.format(locale)

--- a/taskcluster/taskgraph/transforms/task.py
+++ b/taskcluster/taskgraph/transforms/task.py
@@ -31,17 +31,17 @@ from taskgraph.util.schema import (
     taskref_or_string,
 )
 from taskgraph.util.scriptworker import (
     BALROG_ACTIONS,
     get_release_config,
     add_scope_prefix,
 )
 from taskgraph.util.signed_artifacts import get_signed_artifacts
-from voluptuous import Any, Required, Optional, Extra
+from voluptuous import Any, Required, Optional, Extra, Match
 from taskgraph import GECKO, MAX_DEPENDENCIES
 from ..util import docker as dockerutil
 
 RUN_TASK = os.path.join(GECKO, 'taskcluster', 'scripts', 'run-task')
 
 
 @memoize
 def _run_task_suffix():
@@ -104,17 +104,17 @@ task_description_schema = Schema({
         'kind': Any('build', 'test', 'other'),
 
         # tier for this task
         'tier': int,
 
         # task platform, in the form platform/collection, used to set
         # treeherder.machine.platform and treeherder.collection or
         # treeherder.labels
-        'platform': basestring,
+        'platform': Match('^[A-Za-z0-9_-]{1,50}/[A-Za-z0-9_-]{1,50}$'),
     },
 
     # information for indexing this build so its artifacts can be discovered;
     # if omitted, the build will not be indexed.
     Optional('index'): {
         # the name of the product this build produces
         'product': basestring,