diff --git a/src/Lean/Compiler/LCNF/Passes.lean b/src/Lean/Compiler/LCNF/Passes.lean
index 1356a0a4b4..4579073511 100644
--- a/src/Lean/Compiler/LCNF/Passes.lean
+++ b/src/Lean/Compiler/LCNF/Passes.lean
@@ -94,6 +94,7 @@ builtin_initialize passManagerExt : PersistentEnvExtension Name (Name × PassMan
     addImportedFn := fun ns => return ([], ← ImportM.runCoreM <| runImportedDecls ns)
     addEntryFn := fun (installerDeclNames, _) (installerDeclName, managerNew) => (installerDeclName :: installerDeclNames, managerNew)
     exportEntriesFn := fun s => s.1.reverse.toArray
+    asyncMode := .sync
   }
 
 def getPassManager : CoreM PassManager :=
diff --git a/src/Lean/Compiler/LCNF/Simp/ConstantFold.lean b/src/Lean/Compiler/LCNF/Simp/ConstantFold.lean
index b950aec8ba..5551fb028c 100644
--- a/src/Lean/Compiler/LCNF/Simp/ConstantFold.lean
+++ b/src/Lean/Compiler/LCNF/Simp/ConstantFold.lean
@@ -410,6 +410,7 @@ builtin_initialize folderExt : PersistentEnvExtension FolderOleanEntry FolderEnt
       return ([], folders.switch)
     addEntryFn := fun (entries, map) entry => (entry.toFolderOleanEntry :: entries, map.insert entry.declName entry.folder)
     exportEntriesFn := fun (entries, _) => entries.reverse.toArray
+    asyncMode := .sync
   }
 
 def registerFolder (declName : Name) (folderDeclName : Name) : CoreM Unit := do
diff --git a/src/Lean/Compiler/LCNF/SpecInfo.lean b/src/Lean/Compiler/LCNF/SpecInfo.lean
index 8b4468cd47..b63556c355 100644
--- a/src/Lean/Compiler/LCNF/SpecInfo.lean
+++ b/src/Lean/Compiler/LCNF/SpecInfo.lean
@@ -85,6 +85,7 @@ builtin_initialize specExtension : SimplePersistentEnvExtension SpecEntry SpecSt
     addEntryFn    := SpecState.addEntry
     addImportedFn := fun _ => {}
     toArrayFn     := fun s => sortEntries s.toArray
+    asyncMode     := .sync
   }
 
 /--
diff --git a/src/Lean/Compiler/LCNF/Specialize.lean b/src/Lean/Compiler/LCNF/Specialize.lean
index 2c01478708..ec626d3b5f 100644
--- a/src/Lean/Compiler/LCNF/Specialize.lean
+++ b/src/Lean/Compiler/LCNF/Specialize.lean
@@ -32,6 +32,7 @@ builtin_initialize specCacheExt : SimplePersistentEnvExtension CacheEntry Cache
   registerSimplePersistentEnvExtension {
     addEntryFn    := addEntry
     addImportedFn := fun es => (mkStateFromImportedEntries addEntry {} es).switch
+    asyncMode     := .sync
   }
 
 def cacheSpec (key : Expr) (declName : Name) : CoreM Unit :=