diff --git a/Changes.md b/Changes.md
index 116409cbdea..1b927f28753 100644
--- a/Changes.md
+++ b/Changes.md
@@ -24,6 +24,7 @@ Fixes
   - Fixed error when trying to visualise data unsupported data.
 - TweakPlug : Fixed preservation of geometric interpretation when tweaking V3f values.
 - ApplicationTest : Extended grace period when testing process name on slower hosts.
+- OpDialogue : Fixed `DefaultButton` handling.
 
 API
 ---
diff --git a/python/GafferCortexUI/OpDialogue.py b/python/GafferCortexUI/OpDialogue.py
index 3991572113c..0f7dac9a3a3 100644
--- a/python/GafferCortexUI/OpDialogue.py
+++ b/python/GafferCortexUI/OpDialogue.py
@@ -464,11 +464,16 @@ def __focusDefaultButton( self ) :
 			with IECore.IgnoredExceptions( KeyError ) :
 				d = self.__node.getParameterised()[0].userData()["UI"]["defaultButton"]
 			if d is not None :
-				for v in self.DefaultButton.values() :
+				for v in self.DefaultButton :
 					if str( v ).lower() == d.value.lower() :
 						defaultButton = v
 						break
 
+					# backwards compatibility for IECore.Enum()
+					if str( v ).lower() == f"DefaultButton.{d.value}".lower() :
+						defaultButton = v
+						break
+
 		if defaultButton == self.DefaultButton.None_ :
 			self._qtWidget().setFocus()
 		elif defaultButton == self.DefaultButton.Cancel :