--- a/mobile/android/base/java/org/mozilla/gecko/switchboard/SwitchBoard.java
+++ b/mobile/android/base/java/org/mozilla/gecko/switchboard/SwitchBoard.java
@@ -76,16 +76,17 @@ public class SwitchBoard {
     private static final String KEY_DATA = "data";
     private static final String KEY_NAME = "name";
     private static final String KEY_MATCH = "match";
     private static final String KEY_BUCKETS = "buckets";
     private static final String KEY_VALUES = "values";
 
     // Match keys.
     private static final String KEY_APP_ID = "appId";
+    private static final String KEY_LOCALE = "locale";
     private static final String KEY_COUNTRY = "country";
     private static final String KEY_REGION = "regions";
     private static final String KEY_DEVICE = "device";
     private static final String KEY_LANG = "lang";
     private static final String KEY_MANUFACTURER = "manufacturer";
     private static final String KEY_VERSION = "version";
 
     // Bucket keys.
@@ -231,17 +232,33 @@ public class SwitchBoard {
                         && !packageName.matches(expectedAppIdPattern)) {
                     return false;
                 }
             } catch (JSONException e) {
                 Log.e(TAG, "Exception matching appId", e);
             }
         }
 
-        if (matchKeys.has(KEY_COUNTRY)) {
+        // Allows for checking [language_country] locale. See Bug 1437699
+        if (matchKeys.has(KEY_LOCALE)) {
+            try {
+                final String locale = Locale.getDefault().toString();
+                final String expectedLocalePattern = matchKeys.getString(KEY_LOCALE);
+
+                if (!TextUtils.isEmpty(expectedLocalePattern)
+                        && !locale.matches(expectedLocalePattern)) {
+                    return false;
+                }
+            } catch (MissingResourceException | JSONException e) {
+                Log.e(TAG, "Exception matching locale", e);
+            }
+        }
+
+        // Full locale [language_country] means country alone should not be checked
+        if (matchKeys.has(KEY_COUNTRY) && !matchKeys.has(KEY_LOCALE)) {
             try {
                 final String country = Locale.getDefault().getISO3Country();
                 final String expectedCountryPattern = matchKeys.getString(KEY_COUNTRY);
 
                 if (!TextUtils.isEmpty(expectedCountryPattern)
                         && !country.matches(expectedCountryPattern)) {
                     return false;
                 }
@@ -259,17 +276,18 @@ public class SwitchBoard {
                         && !device.matches(expectedDevicePattern)) {
                     return false;
                 }
             } catch (JSONException e) {
                 Log.e(TAG, "Exception matching device", e);
             }
         }
 
-        if (matchKeys.has(KEY_LANG)) {
+        // Full locale [language_country] means language alone should not be checked
+        if (matchKeys.has(KEY_LANG) && !matchKeys.has(KEY_LOCALE)) {
             try {
                 final String lang = Locale.getDefault().getISO3Language();
                 final String expectedLanguagePattern = matchKeys.getString(KEY_LANG);
 
                 if (!TextUtils.isEmpty(expectedLanguagePattern)
                         && !lang.matches(expectedLanguagePattern)) {
                     return false;
                 }