--- a/testing/mozharness/configs/unittests/thunderbird_buildbot.py
+++ b/testing/mozharness/configs/unittests/thunderbird_buildbot.py
@@ -1,9 +1,22 @@
+import platform
+
 # Specify tooltool directory for thunderbird buildbot tests explicitly.
 # The default configuration in `linux_unittest.py` specifies a
 # taskcluster-specific location. Override that here until thunderbird is being
 # built on taskcluster.
 # See https://bugzilla.mozilla.org/show_bug.cgi?id=1356520
 # and https://bugzilla.mozilla.org/show_bug.cgi?id=1371734
 config = {
     "tooltool_cache": "/builds/tooltool_cache",
 }
+
+# Specify virtualenv directory for thunderbird buildbot tests explicitly.
+# The default configuration in `linux_unittest.py` specifies a path that
+# doesn't exist on buildbot. We need to specify the other paths here too, since
+# config entries are overriden wholesale.
+if platform.system() == "Linux":
+    config["exes"] = {
+        "python": "/tools/buildbot/bin/python",
+        "virtualenv": ["/tools/buildbot/bin/python", "/tools/misc-python/virtualenv.py"],
+        "tooltool.py": "/tools/tooltool.py",
+    }