diff --git a/qt/aqt/main.py b/qt/aqt/main.py
index bb1eee453..25ba3311b 100644
--- a/qt/aqt/main.py
+++ b/qt/aqt/main.py
@@ -347,13 +347,24 @@ close the profile or restart Anki."""
     def _on_downgrade(self):
         self.progress.start()
         profiles = self.pm.profiles()
+
         def downgrade():
-            self.pm.downgrade(profiles)
+            return self.pm.downgrade(profiles)
+
         def on_done(future):
             self.progress.finish()
-            future.result()
-            showInfo("Profiles can now be opened with an older version of Anki.")
+            problems = future.result()
+            if not problems:
+                showInfo("Profiles can now be opened with an older version of Anki.")
+            else:
+                showWarning(
+                    "The following profiles could not be downgraded: {}".format(
+                        ", ".join(problems)
+                    )
+                )
+                return
             self.profileDiag.close()
+
         self.taskman.run_in_background(downgrade, on_done)
 
     def loadProfile(self, onsuccess: Optional[Callable] = None) -> None:
@@ -458,7 +469,9 @@ close the profile or restart Anki."""
             self._loadCollection()
         except Exception as e:
             if "FileTooNew" in str(e):
-                showWarning("This profile requires a newer version of Anki to open. Did you forget to use the Downgrade button prior to switching Anki versions?")
+                showWarning(
+                    "This profile requires a newer version of Anki to open. Did you forget to use the Downgrade button prior to switching Anki versions?"
+                )
             else:
                 showWarning(
                     tr(TR.ERRORS_UNABLE_OPEN_COLLECTION) + "\n" + traceback.format_exc()
diff --git a/qt/aqt/profiles.py b/qt/aqt/profiles.py
index d9796ebd6..b8dff8abb 100644
--- a/qt/aqt/profiles.py
+++ b/qt/aqt/profiles.py
@@ -11,7 +11,7 @@ import locale
 import pickle
 import random
 import shutil
-from typing import Any, Dict, Optional, List
+from typing import Any, Dict, List, Optional
 
 from send2trash import send2trash
 
@@ -279,7 +279,9 @@ and no other programs are accessing your profile folders, then try again."""
     # Downgrade
     ######################################################################
 
-    def downgrade(self, profiles=List[str]):
+    def downgrade(self, profiles=List[str]) -> List[str]:
+        "Downgrade all profiles. Return a list of profiles that couldn't be opened."
+        problem_profiles = []
         for name in profiles:
             path = os.path.join(self.base, name, "collection.anki2")
             if not os.path.exists(path):
@@ -288,8 +290,13 @@ and no other programs are accessing your profile folders, then try again."""
                 if db.scalar("select ver from col") == 11:
                     # nothing to do
                     continue
-            c = Collection(path)
-            c.close(save=False, downgrade=True)
+            try:
+                c = Collection(path)
+                c.close(save=False, downgrade=True)
+            except Exception as e:
+                print(e)
+                problem_profiles.append(name)
+        return problem_profiles
 
     # Helpers
     ######################################################################