diff --git a/compiler/GHC/Parser/Lexer.x b/compiler/GHC/Parser/Lexer.x
--- a/compiler/GHC/Parser/Lexer.x
+++ b/compiler/GHC/Parser/Lexer.x
@@ -3474,7 +3474,7 @@
 -- If the generated alexScan/alexScanUser functions are called multiple times
 -- in this file, alexScanUser gets broken out into a separate function and
 -- increases memory usage. Make sure GHC inlines this function and optimizes it.
-{-# INLINE alexScanUser #-}
+
 
 lexToken :: P (PsLocated Token)
 lexToken = do
diff --git a/ghc-lib-parser.cabal b/ghc-lib-parser.cabal
--- a/ghc-lib-parser.cabal
+++ b/ghc-lib-parser.cabal
@@ -1,7 +1,7 @@
 cabal-version: 3.0
 build-type: Simple
 name: ghc-lib-parser
-version: 9.12.1.20250103
+version: 9.12.1.20250105
 license: BSD-3-Clause
 license-file: LICENSE
 category: Development
@@ -119,7 +119,7 @@
         process >= 1 && < 1.7
     if impl(ghc >= 9.10)
       build-depends: ghc-internal
-    build-tool-depends: alex:alex >= 3.1 && < 3.5.2.0, happy:happy == 1.20.* || == 2.0.2 || >= 2.1.2 && < 2.2
+    build-tool-depends: alex:alex >= 3.1, happy:happy == 1.20.* || == 2.0.2 || >= 2.1.2 && < 2.2
     other-extensions:
         BangPatterns
         CPP
diff --git a/ghc-lib/stage0/compiler/build/GHC/Settings/Config.hs b/ghc-lib/stage0/compiler/build/GHC/Settings/Config.hs
--- a/ghc-lib/stage0/compiler/build/GHC/Settings/Config.hs
+++ b/ghc-lib/stage0/compiler/build/GHC/Settings/Config.hs
@@ -22,7 +22,7 @@
 cProjectName          = "The Glorious Glasgow Haskell Compilation System"
 
 cBooterVersion        :: String
-cBooterVersion        = "9.8.4"
+cBooterVersion        = "9.12.1"
 
 cStage                :: String
 cStage                = show (1 :: Int)