diff --git a/common/changes/@microsoft/rush/bugfix-yaml_dump_error_2024-12-23-08-19.json b/common/changes/@microsoft/rush/bugfix-yaml_dump_error_2024-12-23-08-19.json
new file mode 100644
index 00000000000..18f2c148b4d
--- /dev/null
+++ b/common/changes/@microsoft/rush/bugfix-yaml_dump_error_2024-12-23-08-19.json
@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/rush",
+      "comment": "Fix an issue where the lockfile object has a nullish value causing yaml.dump to report an error.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@microsoft/rush"
+}
\ No newline at end of file
diff --git a/libraries/rush-lib/src/logic/pnpm/PnpmShrinkWrapFileConverters.ts b/libraries/rush-lib/src/logic/pnpm/PnpmShrinkWrapFileConverters.ts
index 236afa90610..ca57585da1d 100644
--- a/libraries/rush-lib/src/logic/pnpm/PnpmShrinkWrapFileConverters.ts
+++ b/libraries/rush-lib/src/logic/pnpm/PnpmShrinkWrapFileConverters.ts
@@ -24,6 +24,7 @@ import type {
   ProjectSnapshot,
   ResolvedDependencies
 } from '@pnpm/lockfile.types';
+import { removeNullishProps } from '../../utilities/objectUtilities';
 
 type DepPath = string & { __brand: 'DepPath' };
 // eslint-disable-next-line @typescript-eslint/typedef
@@ -56,11 +57,13 @@ function revertProjectSnapshot(from: InlineSpecifiersProjectSnapshot): ProjectSn
     from.optionalDependencies == null ? from.optionalDependencies : moveSpecifiers(from.optionalDependencies);
 
   return {
-    ...from,
-    specifiers,
-    dependencies,
-    devDependencies,
-    optionalDependencies
+    ...removeNullishProps({
+      ...from,
+      dependencies,
+      devDependencies,
+      optionalDependencies
+    }),
+    specifiers
   };
 }
 
diff --git a/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapConverters.test.ts b/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapConverters.test.ts
index 7234f7721fc..673bf4826ff 100644
--- a/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapConverters.test.ts
+++ b/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapConverters.test.ts
@@ -38,4 +38,15 @@ describe(convertLockfileV9ToLockfileObject.name, () => {
       'pad-left': '^2.1.0'
     });
   });
+
+  it("no nullish values", () => {
+    const importers = new Map<string, ProjectSnapshot>(Object.entries(lockfile.importers || {}));
+
+    const currentPackage = importers.get('.');
+    const props = Object.keys(currentPackage || {});
+    expect(props).toContain('dependencies');
+    expect(props).toContain('specifiers');
+    expect(props).not.toContain('optionalDependencies');
+    expect(props).not.toContain('devDependencies');
+  });
 });
diff --git a/libraries/rush-lib/src/utilities/objectUtilities.ts b/libraries/rush-lib/src/utilities/objectUtilities.ts
index 092ba9ddc18..6224b94dc30 100644
--- a/libraries/rush-lib/src/utilities/objectUtilities.ts
+++ b/libraries/rush-lib/src/utilities/objectUtilities.ts
@@ -153,3 +153,21 @@ function isStrictComparable<T>(value: T): boolean {
     value === value && !(value !== null && value !== undefined && (type === 'object' || type === 'function'))
   );
 }
+
+/**
+ * Removes `undefined` and `null` direct properties from an object.
+ *
+ * @remarks
+ * Note that this does not recurse through sub-objects.
+ */
+export function removeNullishProps<T extends object>(obj: T): Partial<T> {
+  const result: Partial<T> = {};
+  for (const key in obj) {
+    if (obj.hasOwnProperty(key)) {
+      if (obj[key] !== undefined && obj[key] !== null) {
+        result[key] = obj[key];
+      }
+    }
+  }
+  return result;
+}
diff --git a/libraries/rush-lib/src/utilities/test/objectUtilities.test.ts b/libraries/rush-lib/src/utilities/test/objectUtilities.test.ts
index 6b8fef7ad51..9235fd63ab8 100644
--- a/libraries/rush-lib/src/utilities/test/objectUtilities.test.ts
+++ b/libraries/rush-lib/src/utilities/test/objectUtilities.test.ts
@@ -1,7 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
 // See LICENSE in the project root for license information.
 
-import { objectsAreDeepEqual, cloneDeep, merge } from '../objectUtilities';
+import { objectsAreDeepEqual, cloneDeep, merge, removeNullishProps } from '../objectUtilities';
 
 describe('objectUtilities', () => {
   describe(objectsAreDeepEqual.name, () => {
@@ -147,4 +147,12 @@ describe('objectUtilities', () => {
       expect(merge({ a: { b: 1 } }, { a: { c: 2 } })).toEqual({ a: { b: 1, c: 2 } });
     });
   });
+
+  describe(removeNullishProps.name, () => {
+    it('can remove undefined and null properties', () => {
+      expect(removeNullishProps({ a: 1, b: undefined })).toEqual({ a: 1 });
+      expect(removeNullishProps({ a: 1, b: null })).toEqual({ a: 1 });
+      expect(removeNullishProps({ a: 1, b: undefined, c: null })).toEqual({ a: 1 });
+    });
+  });
 });