diff --git a/.changeset/tidy-rivers-marry.md b/.changeset/tidy-rivers-marry.md
new file mode 100644
index 0000000000..547ef49ed7
--- /dev/null
+++ b/.changeset/tidy-rivers-marry.md
@@ -0,0 +1,5 @@
+---
+"@pnpm/core": patch
+---
+
+fix mergeGitBranchLockfiles when merged lockfile is up-to-date
diff --git a/packages/core/src/install/index.ts b/packages/core/src/install/index.ts
index 7931da2c88..bca9dbd2fc 100644
--- a/packages/core/src/install/index.ts
+++ b/packages/core/src/install/index.ts
@@ -330,6 +330,18 @@ export async function mutateModules (
             pruneVirtualStore,
             wantedLockfile: maybeOpts.ignorePackageManifest ? undefined : ctx.wantedLockfile,
           })
+          if (opts.useLockfile && opts.saveLockfile && opts.mergeGitBranchLockfiles) {
+            await writeLockfiles({
+              currentLockfile: ctx.currentLockfile,
+              currentLockfileDir: ctx.virtualStoreDir,
+              wantedLockfile: ctx.wantedLockfile,
+              wantedLockfileDir: ctx.lockfileDir,
+              forceSharedFormat: opts.forceSharedLockfile,
+              useInlineSpecifiersFormat: opts.useInlineSpecifiersLockfileFormat,
+              useGitBranchLockfile: opts.useGitBranchLockfile,
+              mergeGitBranchLockfiles: opts.mergeGitBranchLockfiles,
+            })
+          }
           return projects
         } catch (error: any) { // eslint-disable-line
           if (
diff --git a/packages/core/test/install/gitBranchLockfile.test.ts b/packages/core/test/install/gitBranchLockfile.test.ts
index ba546f29f8..352488e1d5 100644
--- a/packages/core/test/install/gitBranchLockfile.test.ts
+++ b/packages/core/test/install/gitBranchLockfile.test.ts
@@ -3,7 +3,7 @@ import path from 'path'
 import { prepareEmpty, preparePackages } from '@pnpm/prepare'
 import { install, mutateModules } from '@pnpm/core'
 import { testDefaults } from '../utils'
-import { WANTED_LOCKFILE } from '@pnpm/constants'
+import { LOCKFILE_VERSION, WANTED_LOCKFILE } from '@pnpm/constants'
 import { ProjectManifest } from '@pnpm/types'
 import { getCurrentBranch } from '@pnpm/git-utils'
 import writeYamlFile from 'write-yaml-file'
@@ -144,3 +144,75 @@ test('install with --merge-git-branch-lockfiles', async () => {
   expect(fs.existsSync(otherLockfilePath)).toBe(false)
   expect(fs.existsSync(WANTED_LOCKFILE)).toBe(true)
 })
+
+test('install with --merge-git-branch-lockfiles when merged lockfile is up to date', async () => {
+  const project = prepareEmpty()
+
+  // @types/semver installed in the main branch
+  await writeYamlFile(WANTED_LOCKFILE, {
+    dependencies: {
+      '@types/semver': '5.3.31',
+    },
+    lockfileVersion: LOCKFILE_VERSION,
+    packages: {
+      '/@types/semver/5.3.31': {
+        resolution: {
+          integrity: 'sha512-WBv5F9HrWTyG800cB9M3veCVkFahqXN7KA7c3VUCYZm/xhNzzIFiXiq+rZmj75j7GvWelN3YNrLX7FjtqBvhMw==',
+        },
+      },
+    },
+    specifiers: {
+      '@types/semver': '5.3.31',
+    },
+  }, { lineWidth: 1000 })
+
+  const branchName: string = 'main-branch'
+  getCurrentBranch['mockReturnValue'](branchName)
+
+  // is-positive installed in the other branch
+  const otherLockfilePath: string = path.resolve('pnpm-lock.other.yaml')
+  const otherLockfileContent = {
+    dependencies: {
+      '@types/semver': '5.3.31',
+      'is-positive': '3.1.0',
+    },
+    lockfileVersion: LOCKFILE_VERSION,
+    packages: {
+      '/@types/semver/5.3.31': {
+        resolution: {
+          integrity: 'sha512-WBv5F9HrWTyG800cB9M3veCVkFahqXN7KA7c3VUCYZm/xhNzzIFiXiq+rZmj75j7GvWelN3YNrLX7FjtqBvhMw==',
+        },
+      },
+      '/is-positive/3.1.0': {
+        resolution: {
+          integrity: 'sha512-8ND1j3y9/HP94TOvGzr69/FgbkX2ruOldhLEsTWwcJVfo4oRjwemJmJxt7RJkKYH8tz7vYBP9JcKQY8CLuJ90Q==',
+        },
+      },
+    },
+    specifiers: {
+      '@types/semver': '5.3.31',
+      'is-positive': '^3.1.0',
+    },
+  }
+  await writeYamlFile(otherLockfilePath, otherLockfileContent, { lineWidth: 1000 })
+
+  // the other branch merged to the main branch
+  const projectManifest: ProjectManifest = {
+    dependencies: {
+      '@types/semver': '5.3.31',
+      'is-positive': '^3.1.0',
+    },
+  }
+  const opts = await testDefaults({
+    useGitBranchLockfile: true,
+    mergeGitBranchLockfiles: true,
+    frozenLockfile: true,
+  })
+  await install(projectManifest, opts)
+
+  expect(fs.existsSync(otherLockfilePath)).toBe(false)
+  expect(fs.existsSync(WANTED_LOCKFILE)).toBe(true)
+
+  const wantedLockfileAfterMergeOther = await project.readLockfile()
+  expect(wantedLockfileAfterMergeOther).toEqual(otherLockfileContent)
+})