--- a/hgext/firefoxtree/__init__.py
+++ b/hgext/firefoxtree/__init__.py
@@ -90,16 +90,17 @@ from mercurial.node import (
 
 OUR_DIR = os.path.dirname(__file__)
 execfile(os.path.join(OUR_DIR, '..', 'bootstrap.py'))
 
 from mozautomation.repository import (
     MULTI_TREE_ALIASES,
     resolve_trees_to_uris,
     resolve_uri_to_tree,
+    TRY_TREES,
 )
 
 testedwith = '3.3 3.4 3.5 3.6'
 buglink = 'https://bugzilla.mozilla.org/enter_bug.cgi?product=Developer%20Services&component=Mercurial%3A%20firefoxtree'
 # The root revisions in mozilla-central and comm-central, respectively.
 MOZ_ROOT_REV = '8ba995b74e18334ab3707f27e9eb8f4e37ba3d29'
 COMM_ROOT_REV = 'e4f4569d451a5e0d12a6aa33ebd916f979dd8faa'
 
@@ -221,26 +222,35 @@ def readfirefoxtrees(repo):
         return trees
 
     for line in data.splitlines():
         line = line.strip()
         if not line:
             continue
 
         tree, hexnode = line.split()
+
+        # Filter out try repos because they are special.
+        if tree in TRY_TREES:
+            continue
+
         trees[tree] = bin(hexnode)
 
     return trees
 
 
 def writefirefoxtrees(repo):
     """Write the firefoxtrees node mapping to the filesystem."""
     lines = []
     trees = {}
     for tree, node in sorted(repo.firefoxtrees.items()):
+        # Filter out try repos because they are special.
+        if tree in TRY_TREES:
+            continue
+
         assert len(node) == 20
         lines.append('%s %s' % (tree, hex(node)))
         trees[tree] = hex(node)
 
     _firefoxtreesrepo(repo).vfs.write('firefoxtrees', '\n'.join(lines))
 
     # Old versions of firefoxtrees stored labels in the localtags file. Since
     # this file is read by Mercurial and has no relevance to us any more, we
@@ -380,16 +390,20 @@ def updateremoterefs(repo, remote, tree)
     Firefox repos.
     """
     # TODO Somehow the custom repo class is lost and the firefoxtrees attribute
     # isn't accessible. This is possibly a result of repo filter and/or clone
     # bundles interaction. See bug 1234396.
     if getattr(repo, 'firefoxtrees', None) is None:
         return
 
+    # Ignore try repos because they are special.
+    if tree in TRY_TREES:
+        return
+
     # We only care about the default branch. We could import
     # RELBRANCH and other branches if we really cared about it.
     # Maybe later.
     branchmap = remote.branchmap()
     if 'default' not in branchmap:
         return
 
     # Firefox repos should only ever have a single head in the

--- a/hgext/firefoxtree/tests/test-tree-tags.t
+++ b/hgext/firefoxtree/tests/test-tree-tags.t
@@ -93,8 +93,31 @@ hg fxheads revset gives known tree commi
 {fxheads} with multiple values
 
   $ hg -q pull b2ginbound
   $ hg log -T '{rev} {join(fxheads, " ")}\n'
   3 inbound
   2 
   1 b2ginbound central
   0 
+
+"try" is filtered from firefoxtrees
+
+  $ cat >> .hg/firefoxtrees << EOF
+  > 
+  > try 994ec05999daf04fb3c01a8cb0dea1458a7d4d3d
+  > EOF
+
+  $ hg pull fxtrees
+  pulling from b2ginbound
+  searching for changes
+  no changes found
+  pulling from central
+  searching for changes
+  no changes found
+  pulling from inbound
+  searching for changes
+  no changes found
+
+  $ cat .hg/firefoxtrees
+  b2ginbound 994ec05999daf04fb3c01a8cb0dea1458a7d4d3d
+  central 994ec05999daf04fb3c01a8cb0dea1458a7d4d3d
+  inbound 1b348279b0e9b3c29568b6abc8a1776a68d39261 (no-eol)

--- a/pylib/mozautomation/mozautomation/repository.py
+++ b/pylib/mozautomation/mozautomation/repository.py
@@ -157,16 +157,21 @@ RELEASE_TREES = set([
     'b2g32',
     'b2g34',
     'b2g37',
     'b2g44',
     'b2g-ota',
 ])
 
 
+TRY_TREES = set([
+    'try',
+    'try-comm',
+])
+
 def resolve_trees_to_official(trees):
     mapped = []
     for tree in trees:
         mapped.extend(TREE_ALIASES.get(tree, [tree]))
     mapped = [OFFICIAL_MAP.get(tree, tree) for tree in mapped]
 
     return mapped