diff --git a/src/Model/Migration.hs b/src/Model/Migration.hs
index 98652d070..30614eaae 100644
--- a/src/Model/Migration.hs
+++ b/src/Model/Migration.hs
@@ -79,16 +79,27 @@ customMigrations :: MonadIO m => Map (Key AppliedMigration) (ReaderT SqlBackend
 customMigrations = Map.fromListWith (>>)
   [ ( AppliedMigrationKey [migrationVersion|initial|] [version|0.0.0|]
     , do -- New theme format
-        userThemes <- [sqlQQ| SELECT @{UserId}, @{UserTheme} FROM ^{User}; |]
-        forM_ userThemes $ \(uid, Single str) -> case stripPrefix "theme--" str of
-          Just v
-            | Just theme <- fromPathPiece v -> update uid [UserTheme =. theme]
-          other -> error $ "Could not parse theme: " <> show other
+        haveUserTable <- [sqlQQ| SELECT to_regclass('user'); |]
+
+        case haveUserTable :: [Maybe (Single Text)] of
+          [Just _] -> do
+            userThemes <- [sqlQQ| SELECT 'id', 'theme' FROM 'user'; |]
+            forM_ userThemes $ \(uid, Single str) -> case stripPrefix "theme--" str of
+              Just v
+                | Just theme <- fromPathPiece v -> update uid [UserTheme =. theme]
+              other -> error $ "Could not parse theme: " <> show other
+          _other -> return ()
     )
   , ( AppliedMigrationKey [migrationVersion|0.0.0|] [version|1.0.0|]
-    , [executeQQ| -- Better JSON encoding
-        ALTER TABLE "sheet" ALTER COLUMN "type" TYPE json USING "type"::json;
-        ALTER TABLE "sheet" ALTER COLUMN "grouping" TYPE json USING "grouping"::json;
-      |]
+    , do -- Better JSON encoding
+        haveSheetTable <- [sqlQQ| SELECT to_regclass('sheet'); |]
+
+        case haveSheetTable :: [Maybe (Single Text)] of
+          [Just _] ->
+            [executeQQ|
+              ALTER TABLE 'sheet' ALTER COLUMN 'type' TYPE json USING 'type'::json;
+              ALTER TABLE 'sheet' ALTER COLUMN 'grouping' TYPE json USING 'grouping'::json;
+            |]
+          _other -> return ()
     )
   ]