diff --git a/contentcuration/contentcuration/tests/utils/test_exercise_creation.py b/contentcuration/contentcuration/tests/utils/test_exercise_creation.py
index d9cd3add1b..ae6a295e41 100644
--- a/contentcuration/contentcuration/tests/utils/test_exercise_creation.py
+++ b/contentcuration/contentcuration/tests/utils/test_exercise_creation.py
@@ -1603,7 +1603,7 @@ def test_free_response_question_with_maths(self):
             <math display="block">
                 <semantics>
                     <mrow>
-                        <msubsup><mo>∑</mo><mi>n</mi><mi>s</mi></msubsup>
+                        <munderover><mo>∑</mo><mi>n</mi><mi>s</mi></munderover>
                         <mi>x</mi>
                         <msup><mi>a</mi><mi>n</mi></msup>
                     </mrow>
diff --git a/contentcuration/contentcuration/tests/utils/test_markdown.py b/contentcuration/contentcuration/tests/utils/test_markdown.py
index c111146a85..0088d4a09e 100644
--- a/contentcuration/contentcuration/tests/utils/test_markdown.py
+++ b/contentcuration/contentcuration/tests/utils/test_markdown.py
@@ -120,8 +120,8 @@ def test_mixed_inline_and_block(self):
             "</p>\n"
             "<p>And this is block math:</p>\n"
             '<math display="block">'
-            "<semantics><mrow><msubsup><mo>∑</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow>"
-            "<mi>n</mi></mrow></msubsup><msub><mi>x</mi><mi>i</mi></msub><mo>=</mo><mi>y</mi></mrow>"
+            "<semantics><mrow><munderover><mo>∑</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow>"
+            "<mi>n</mi></mrow></munderover><msub><mi>x</mi><mi>i</mi></msub><mo>=</mo><mi>y</mi></mrow>"
             '<annotation encoding="application/x-tex">\sum_{i=1}^{n} x_i = y</annotation></semantics>'  # noqa W605
             "</math>"
             "<p>Back to text with more inline: "
@@ -132,6 +132,62 @@ def test_mixed_inline_and_block(self):
 
         self._assert_conversion(markdown_text, expected)
 
+    def test_block_sum_uses_munderover(self):
+        """Block-mode \\sum with sub+superscript must use <munderover>, not <msubsup>"""
+
+        markdown_text = "$$\\sum_{i=1}^{n} x_i$$"
+        expected = (
+            '<math display="block">'
+            "<semantics><mrow><munderover><mo>∑</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow>"
+            "<mi>n</mi></mrow></munderover><msub><mi>x</mi><mi>i</mi></msub></mrow>"
+            '<annotation encoding="application/x-tex">\\sum_{i=1}^{n} x_i</annotation></semantics>'
+            "</math>"
+        )
+
+        self._assert_conversion(markdown_text, expected)
+
+    def test_inline_sum_uses_msubsup(self):
+        """Inline-mode \\sum with sub+superscript must use <msubsup>, not <munderover>"""
+
+        markdown_text = "The sum $$\\sum_{i=1}^{n} x_i$$ is finite."
+        expected = (
+            "<p>The sum "
+            '<math display="inline"><semantics><mrow><msubsup><mo>∑</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow>'
+            "<mi>n</mi></mrow></msubsup><msub><mi>x</mi><mi>i</mi></msub></mrow>"
+            '<annotation encoding="application/x-tex">\\sum_{i=1}^{n} x_i</annotation></semantics></math>'
+            " is finite.</p>\n"
+        )
+
+        self._assert_conversion(markdown_text, expected)
+
+    def test_block_prod_uses_munderover(self):
+        """Block-mode \\prod with sub+superscript must use <munderover>"""
+
+        markdown_text = "$$\\prod_{k=0}^{n} a_k$$"
+        expected = (
+            '<math display="block">'
+            "<semantics><mrow><munderover><mo>∏</mo><mrow><mi>k</mi><mo>=</mo><mn>0</mn></mrow><mrow>"
+            "<mi>n</mi></mrow></munderover><msub><mi>a</mi><mi>k</mi></msub></mrow>"
+            '<annotation encoding="application/x-tex">\\prod_{k=0}^{n} a_k</annotation></semantics>'
+            "</math>"
+        )
+
+        self._assert_conversion(markdown_text, expected)
+
+    def test_block_int_unaffected(self):
+        """Block-mode \\int should still use <msubsup> (not affected by munderover fix)"""
+
+        markdown_text = "$$\\int_{a}^{b} f(x) dx$$"
+        expected = (
+            '<math display="block">'
+            "<semantics><mrow><msubsup><mo>∫</mo><mrow><mi>a</mi></mrow><mrow>"
+            '<mi>b</mi></mrow></msubsup><mi>f</mi><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo><mi>d</mi><mi>x</mi></mrow>'
+            '<annotation encoding="application/x-tex">\\int_{a}^{b} f(x) dx</annotation></semantics>'
+            "</math>"
+        )
+
+        self._assert_conversion(markdown_text, expected)
+
     def test_no_math_content(self):
         """Test that regular markdown without math still works"""
 
diff --git a/requirements.in b/requirements.in
index a245b120b0..ff3997361e 100644
--- a/requirements.in
+++ b/requirements.in
@@ -36,5 +36,5 @@ packaging>=21.0
 pycountry
 langcodes==3.5.1
 pydantic==2.12.5
-latex2mathml==3.78.0
+latex2mathml==3.78.1
 markdown-it-py==4.0.0
diff --git a/requirements.txt b/requirements.txt
index b39caf151f..fc0ebd636c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -175,7 +175,7 @@ kombu==5.6.1
     # via celery
 langcodes==3.5.1
     # via -r requirements.in
-latex2mathml==3.78.0
+latex2mathml==3.78.1
     # via -r requirements.in
 le-utils==0.2.12
     # via -r requirements.in