diff --git a/tuskar_ui/forms.py b/tuskar_ui/forms.py
index eb892fc3d..e5aab2043 100644
--- a/tuskar_ui/forms.py
+++ b/tuskar_ui/forms.py
@@ -97,15 +97,19 @@ class MultiMACField(forms.fields.Field):
 
     def clean(self, value):
         value = super(MultiMACField, self).clean(value)
-        try:
-            macs = []
-            for mac in SEPARATOR_RE.split(value):
-                if mac:
-                    macs.append(normalize_MAC(mac))
-            return ' '.join(macs)
-        except ValueError:
-            raise forms.ValidationError(
-                _(u'%r is not a valid MAC address.') % mac)
+
+        macs = []
+        for mac in SEPARATOR_RE.split(value):
+            if mac:
+                try:
+                    normalized_mac = normalize_MAC(mac)
+                except ValueError:
+                    raise forms.ValidationError(
+                        _(u'%r is not a valid MAC address.') % mac)
+                else:
+                    macs.append(normalized_mac)
+
+        return ' '.join(sorted(set(macs)))
 
 
 class NetworkField(forms.fields.Field):
diff --git a/tuskar_ui/test/test_forms.py b/tuskar_ui/test/test_forms.py
index 0da52d703..9b9a0cd3f 100644
--- a/tuskar_ui/test/test_forms.py
+++ b/tuskar_ui/test/test_forms.py
@@ -57,3 +57,12 @@ class MultiMACFieldTests(test.TestCase):
             "DE:AD:BE:EF:CA:FC DE:AD:BE:EF:CA:FD DE:AD:BE:EF:CA:FE "
             "DE:AD:BE:EF:CA:FF",
         )
+
+    def test_duplicated(self):
+        field = forms.MultiMACField(required=False)
+        cleaned = field.clean("DE:AD:BE:EF:CA:FC DE:AD:BE:EF:CA:FC")
+
+        self.assertEqual(
+            cleaned,
+            "DE:AD:BE:EF:CA:FC",
+        )