diff --git a/testing/mozbase/moztest/moztest/resolve.py b/testing/mozbase/moztest/moztest/resolve.py
index bd56d350942d..37e14d0038b0 100644
--- a/testing/mozbase/moztest/moztest/resolve.py
+++ b/testing/mozbase/moztest/moztest/resolve.py
@@ -13,12 +13,11 @@ from collections import defaultdict
 import manifestparser
 import mozpack.path as mozpath
 from mozbuild.base import MozbuildObject
-from mozbuild.util import OrderedDefaultDict
 from mozbuild.frontend.reader import BuildReader, EmptyConfig
+from mozbuild.util import OrderedDefaultDict
 
 here = os.path.abspath(os.path.dirname(__file__))
 
-
 MOCHITEST_CHUNK_BY_DIR = 4
 MOCHITEST_TOTAL_CHUNKS = 5
 
@@ -333,6 +332,7 @@ class TestMetadata(object):
         self._tests_by_flavor = defaultdict(set)
         self._test_dirs = set()
         self._objdir = os.path.abspath(os.path.join(all_tests, os.pardir))
+        self._puppeteer_loaded = False
         self._wpt_loaded = False
         self._srcdir = srcdir
 
@@ -461,6 +461,9 @@ class TestMetadata(object):
         return mozpath.match(path, "remote/test/puppeteer/test/**")
 
     def add_puppeteer_manifest_data(self):
+        if self._puppeteer_loaded:
+            return
+
         test_path = os.path.join(self._srcdir, "remote", "test", "puppeteer", "test")
         for root, dirs, paths in os.walk(test_path):
             for filename in fnmatch.filter(paths, "*.spec.js"):
@@ -479,6 +482,8 @@ class TestMetadata(object):
                     "srcdir_relpath": path,
                     })
 
+        self._puppeteer_loaded = True
+
     def is_wpt_path(self, path):
         if path is None:
             return True
diff --git a/testing/mozbase/moztest/tests/test_resolve.py b/testing/mozbase/moztest/tests/test_resolve.py
index 11c1de61100f..4b3c4b7da8d2 100644
--- a/testing/mozbase/moztest/tests/test_resolve.py
+++ b/testing/mozbase/moztest/tests/test_resolve.py
@@ -220,7 +220,9 @@ class Base(unittest.TestCase):
         self._temp_files.append(test_defaults)
 
         rv = TestMetadata(all_tests.name, "/firefox/", test_defaults=test_defaults.name)
-        rv._wpt_loaded = True  # Don't try to load the wpt manifest
+        # Avoid loading wpt or puppeteer manifests.
+        rv._wpt_loaded = True
+        rv._puppeteer_loaded = True
         return rv