diff --git a/src/main/browser/browser-cookie-import-clear.ts b/src/main/browser/browser-cookie-import-clear.ts
index 369ad5d432d..4cca8b739ba 100644
--- a/src/main/browser/browser-cookie-import-clear.ts
+++ b/src/main/browser/browser-cookie-import-clear.ts
@@ -84,7 +84,10 @@ export async function withCookieClearLock<T>(owner: object, run: () => Promise<T
   }
 }
 
-function removableCookieEntries(cookies: readonly Cookie[]): { cookie: Cookie; url: string }[] {
+function removableCookieEntries(
+  cookies: readonly Cookie[],
+  requireAddressable = false
+): { cookie: Cookie; url: string }[] {
   const removable: { cookie: Cookie; url: string }[] = []
   for (const cookie of cookies) {
     if (isNonTransplantableCookieDomain(cookie.domain ?? '')) {
@@ -93,6 +96,9 @@ function removableCookieEntries(cookies: readonly Cookie[]): { cookie: Cookie; u
     const domain = cookie.domain ? normalizeCookieDomain(cookie.domain) : null
     const url = domain ? cookieRemovalUrl(cookie, domain) : null
     if (!url) {
+      if (requireAddressable) {
+        throw new Error('Could not clear existing cookies; the session was left unchanged')
+      }
       continue
     }
     removable.push({ cookie, url })
@@ -154,7 +160,7 @@ export async function removeTransplantableCookies(
       return
     }
 
-    const initialRemovable = removableCookieEntries(initialCookies)
+    const initialRemovable = removableCookieEntries(initialCookies, true)
     const identities = await targetSession.snapshotClearIdentities(initialRemovable)
     assertClearIdentitiesCoverRemovable(initialRemovable, identities)
 
diff --git a/src/main/browser/browser-cookie-import-policy.test.ts b/src/main/browser/browser-cookie-import-policy.test.ts
index ad83fd75950..aac8641ff69 100644
--- a/src/main/browser/browser-cookie-import-policy.test.ts
+++ b/src/main/browser/browser-cookie-import-policy.test.ts
@@ -289,14 +289,16 @@ describe('removeTransplantableCookies', () => {
     expect(remove).not.toHaveBeenCalled()
   })
 
-  it('bulk clears cookies the per-cookie path could never address', async () => {
-    const { session, clearData } = clearSession([
+  it('does not mutate when a transplantable cookie cannot be represented for rollback', async () => {
+    const { session, clearData, remove, restoreClearIdentities } = clearSession([
       { ...cookie('.example.com', 'session'), domain: '' }
     ])
 
-    await removeTransplantableCookies(session)
+    await expect(removeTransplantableCookies(session)).rejects.toThrow(/session was left unchanged/)
 
-    expect(clearData).toHaveBeenCalledOnce()
+    expect(clearData).not.toHaveBeenCalled()
+    expect(remove).not.toHaveBeenCalled()
+    expect(restoreClearIdentities).not.toHaveBeenCalled()
   })
 
   it('falls back to per-cookie removal when the bulk clear rejects', async () => {