diff --git a/django/utils/translation/trans_real.py b/django/utils/translation/trans_real.py
index 48ed7cc885..6e7fb8cf50 100644
--- a/django/utils/translation/trans_real.py
+++ b/django/utils/translation/trans_real.py
@@ -40,6 +40,9 @@ def to_locale(language, to_lower=False):
         if to_lower:
             return language[:p].lower()+'_'+language[p+1:].lower()
         else:
+            # Get correct locale for sr-latn
+            if len(language[p+1:]) > 2:
+                return language[:p].lower()+'_'+language[p+1].upper()+language[p+2:].lower()
             return language[:p].lower()+'_'+language[p+1:].upper()
     else:
         return language.lower()
diff --git a/tests/regressiontests/i18n/tests.py b/tests/regressiontests/i18n/tests.py
index 94e792cf54..d97ff31d48 100644
--- a/tests/regressiontests/i18n/tests.py
+++ b/tests/regressiontests/i18n/tests.py
@@ -4,7 +4,7 @@ import misc
 regressions = ur"""
 Format string interpolation should work with *_lazy objects.
 
->>> from django.utils.translation import ugettext, ugettext_lazy, activate, deactivate, gettext_lazy
+>>> from django.utils.translation import ugettext, ugettext_lazy, activate, deactivate, gettext_lazy, to_locale
 >>> s = ugettext_lazy('Add %(name)s')
 >>> d = {'name': 'Ringo'}
 >>> s % d
@@ -17,6 +17,21 @@ u'Ringo hinzuf\xfcgen'
 u'Dodaj Ringo'
 >>> deactivate()
 
+Tests the to_locale function and the special case of Serbian Latin (refs #12230 and r11299)
+
+>>> to_locale('en-us')
+'en_US'
+>>> to_locale('sr-lat')
+'sr_Lat'
+
+Test the to_language function
+
+>>> from django.utils.translation.trans_real import to_language
+>>> to_language('en_US')
+'en-us'
+>>> to_language('sr_Lat')
+'sr-lat'
+
 It should be possible to compare *_lazy objects.
 
 >>> s1 = ugettext_lazy('Add %(name)s')