diff --git a/packages/models/src/sql/normalize.js b/packages/models/src/sql/normalize.js
index 357096a5d3..e63f32a43a 100644
--- a/packages/models/src/sql/normalize.js
+++ b/packages/models/src/sql/normalize.js
@@ -92,6 +92,13 @@ function detectUnmatchedPairs(obfuscated, adapter) {
  * @returns {string}
  */
 export default function normalize(sql, adapter) {
+  // The MongoDB agents record each operation as a statement whose argument
+  // values are already replaced with placeholders, for example
+  // db.users.updateOne({"_id": ?}, {"$set": {"name": ?}}). The generic
+  // obfuscation below would treat the quoted keys as string literals and a
+  // pair of $operators as a dollar-quoted string, so leave it as it is.
+  if (adapter === 'mongodb') return sql;
+
   /** @type {RegExp[]} */ let regexp;
   switch (adapter) {
     case 'mysql':
diff --git a/packages/models/tests/unit/sql.normalize.spec.js b/packages/models/tests/unit/sql.normalize.spec.js
new file mode 100644
index 0000000000..17f4b4c6c9
--- /dev/null
+++ b/packages/models/tests/unit/sql.normalize.spec.js
@@ -0,0 +1,28 @@
+import normalize from '../../src/sql/normalize';
+
+describe('normalize SQL', () => {
+  test('replaces literals for a known dialect', () => {
+    expect(normalize("SELECT * FROM users WHERE id = 1 AND name = 'bob'", 'postgres')).toEqual(
+      'SELECT * FROM users WHERE id = ? AND name = ?'
+    );
+  });
+
+  test('replaces literals with the fallback for an unknown dialect', () => {
+    expect(normalize('SELECT * FROM users WHERE id = 1', 'something')).toEqual(
+      'SELECT * FROM users WHERE id = ?'
+    );
+  });
+
+  test('leaves MongoDB statements alone, since the agent already normalized them', () => {
+    const statements = [
+      'db.users.find({"a": ?})',
+      'db.users.updateOne({"_id": ?}, {"$set": {"name": ?}, "$inc": {"n": ?}}, {"upsert": ?})',
+      'db.orders.aggregate([{"$match": {"status": ?}}, {"$group": {"_id": ?, "total": {"$sum": ?}}}])',
+      'db.getCollection("with-dash").insertOne({"a": ?})',
+      'db.users.distinct("email", {"deleted": ?})',
+    ];
+    statements.forEach((statement) => {
+      expect(normalize(statement, 'mongodb')).toEqual(statement);
+    });
+  });
+});