diff --git a/source/reference/operator/query/mod.txt b/source/reference/operator/query/mod.txt
index 147fcbdd54c..0855b6c3cfb 100644
--- a/source/reference/operator/query/mod.txt
+++ b/source/reference/operator/query/mod.txt
@@ -21,20 +21,22 @@ $mod
 
       { field: { $mod: [ divisor, remainder ] } }
 
+.. _mod-behavior:
+
 Behavior
 --------
 
-The :query:`$mod` operator returns an error if the:
-
-- ``[ divisor, remainder ]`` array contains fewer or more than
-  two elements. For examples, see :ref:`mod-not-enough-elements` and
-  :ref:`mod-too-many-elements` respectively.
+The :query:`$mod` operator returns an error if the  ``[ divisor,
+remainder ]`` array contains fewer or more than two elements. For
+examples, see :ref:`mod-not-enough-elements` and
+:ref:`mod-too-many-elements` respectively.
 
-- ``divisor`` or ``remainder`` values evaluate to:
+Also, starting in MongoDB 5.1 (and 5.0.4 and 4.4.10), :query:`$mod`
+returns an error if the ``divisor`` or ``remainder`` values evaluate to:
 
-  - ``NaN`` (not a number) or ``Infinity``.
+- ``NaN`` (not a number) or ``Infinity``.
 
-  - A value that cannot be represented using a 64-bit integer.
+- A value that cannot be represented using a 64-bit integer.
 
 Examples
 --------
diff --git a/source/release-notes/5.1-compatibility.txt b/source/release-notes/5.1-compatibility.txt
index f06bb4dd442..c3ce44fdd2f 100644
--- a/source/release-notes/5.1-compatibility.txt
+++ b/source/release-notes/5.1-compatibility.txt
@@ -68,6 +68,13 @@ Auditing
 General Changes
 ---------------
 
+``$mod`` Error Behavior
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Starting in MongoDB 5.1 (and 5.0.4 and 4.4.10), the :query:`$mod`
+operator returns an error if the ``divisor`` or ``remainder`` values
+evaluate to certain values. See :ref:`$mod behavior <mod-behavior>`.
+
 Deprecations
 ------------