diff --git a/novelwriter/core/project.py b/novelwriter/core/project.py
index f018cfd7..69aaadcf 100644
--- a/novelwriter/core/project.py
+++ b/novelwriter/core/project.py
@@ -356,6 +356,7 @@ class NWProject:
         self.setProjectChanged(False)
         self._valid = True
         self._state = NWProjectState.READY
+        self._storage.lockSession()  # Lock only after a successful open. See issue #1977.
 
         SHARED.newStatusMessage(self.tr("Opened Project: {0}").format(self._data.name))
 
diff --git a/novelwriter/core/storage.py b/novelwriter/core/storage.py
index 258c379c..73a3bcb5 100644
--- a/novelwriter/core/storage.py
+++ b/novelwriter/core/storage.py
@@ -235,7 +235,6 @@ class NWStorage:
             if child.is_dir() and child.name.startswith("data_"):
                 legacy.legacyDataFolder(basePath, child)
 
-        self._writeLockFile()
         self._ready = True
 
         return NWStorageOpen.READY
@@ -249,6 +248,12 @@ class NWStorage:
             return True
         return True
 
+    def lockSession(self) -> None:
+        """Lock the session when the project is successfully opened."""
+        if self._ready:
+            self._writeLockFile()
+        return
+
     def closeSession(self) -> None:
         """Run tasks related to closing the session."""
         self._clearLockFile()
diff --git a/tests/test_core/test_core_storage.py b/tests/test_core/test_core_storage.py
index ee6e50a0..76be9679 100644
--- a/tests/test_core/test_core_storage.py
+++ b/tests/test_core/test_core_storage.py
@@ -142,7 +142,9 @@ def testCoreStorage_InitProjectStorage(monkeypatch, mockGUI, fncPath, mockRnd):
     storage.clear()
 
     # Open twice, where second should fail due to lockfile
+    # Note that locking is only possible after a successful open
     assert storage.initProjectStorage(fncPath) == NWStorageOpen.READY
+    storage.lockSession()
     assert storage.initProjectStorage(fncPath) == NWStorageOpen.LOCKED
     assert isinstance(storage.lockStatus, list)
     assert len(storage.lockStatus) == 4