--- a/mobile/android/config/mozconfigs/common
+++ b/mobile/android/config/mozconfigs/common
@@ -47,28 +47,40 @@ fi
 ac_add_options --with-android-version=9
 ac_add_options --with-system-zlib
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 
 # Treat warnings as errors (modulo ALLOW_COMPILER_WARNINGS).
 ac_add_options --enable-warnings-as-errors
 
 ac_add_options --with-mozilla-api-keyfile=/builds/mozilla-fennec-geoloc-api.key
+
+# Note: bug 1275669 adds code to prevent adjust pings in CI.
+#
+# MOZ_UPDATE_CHANNEL is only specified for release builds and not CI (e.g.
+# treeherder) builds, even on the beta & release channels. Therefore, all CI
+# builds are expected to use the default keyfile.
+#
+# Even though we don't upload in automation, the default keyfile is necessary
+# because the release & beta release/CI builds specify MOZ_INSTALL_TRACKING &
+# an assertion is thrown if a keyfile is not specified with that env var
+# specified.
+#
+# Ideally, CI builds would set MOZ_UPDATE_CHANNEL & we could remove the default
+# keyfile. This may occur if fennec moves to the release promotion model.
+#
+# Having a default keyfile has the disadvantage that if our beta/release checks
+# ever fail, we'll come to the default case and use the sandbox token instead
+# of asserting that no adjust token is specified. I don't have any better
+# alternatives at the moment.
 if test "$MOZ_UPDATE_CHANNEL" = "release" ; then
     ac_add_options --with-adjust-sdk-keyfile=/builds/adjust-sdk.token
 elif test "$MOZ_UPDATE_CHANNEL" = "beta" ; then
     ac_add_options --with-adjust-sdk-keyfile=/builds/adjust-sdk-beta.token
 else
-    # (bug 1277553) In Aurora -> Beta simulation builds, no update channel is
-    # specified, causing an assertion to throw that MOZ_INSTALL_TRACKING is
-    # specified but the keyfile is not. In this case, we add a default keyfile.
-    # This has the disadvantage that if our beta/release checks above ever
-    # fail, we'll come to this default case and the compile-time check to
-    # specify a valid keyfile will be broken. I don't have any better
-    # alternatives.
     ac_add_options --with-adjust-sdk-keyfile="$topsrcdir/mobile/android/base/adjust-sdk-sandbox.token"
 fi
 export SOCORRO_SYMBOL_UPLOAD_TOKEN_FILE=/builds/crash-stats-api.token
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
 
 # Use ccache