diff --git a/CHANGES b/CHANGES
index c905dc0be..e95feb529 100644
--- a/CHANGES
+++ b/CHANGES
@@ -37,6 +37,7 @@ Bugs fixed
 * #147: Problem with latex chapter style
 * #3018: LaTeX problem with page layout dimensions and chapter titles
 * Fix an issue with ``\pysigline`` in LaTeX style file (ref #3023)
+* #3038: ``sphinx.ext.math*`` raises TypeError if labels are duplicated
 
 Documentation
 -------------
diff --git a/sphinx/ext/mathbase.py b/sphinx/ext/mathbase.py
index 57bcb1c0c..ae4b439b7 100644
--- a/sphinx/ext/mathbase.py
+++ b/sphinx/ext/mathbase.py
@@ -209,7 +209,7 @@ class MathDirective(Directive):
             self.state.document.note_explicit_target(target)
             ret.insert(0, target)
         except UserWarning as exc:
-            self.state_machine.reporter.warning(exc[0], line=self.lineno)
+            self.state_machine.reporter.warning(exc.args[0], line=self.lineno)
 
 
 def latex_visit_math(self, node):