diff --git a/clang/include/clang/Frontend/CompilerInstance.h b/clang/include/clang/Frontend/CompilerInstance.h
index f21f5c29db3a1..ad1c2cfdb2430 100644
--- a/clang/include/clang/Frontend/CompilerInstance.h
+++ b/clang/include/clang/Frontend/CompilerInstance.h
@@ -1040,7 +1040,7 @@ class CompilerInstance : public ModuleLoader {
 
   std::pair<std::shared_ptr<llvm::cas::ObjectStore>,
             std::shared_ptr<llvm::cas::ActionCache>>
-  createCASDatabases();
+  getOrCreateCASDatabases();
 };
 
 } // end namespace clang
diff --git a/clang/lib/Frontend/CompileJobCache.cpp b/clang/lib/Frontend/CompileJobCache.cpp
index f5f45b47f2d0c..84e3ab22bc5b8 100644
--- a/clang/lib/Frontend/CompileJobCache.cpp
+++ b/clang/lib/Frontend/CompileJobCache.cpp
@@ -296,7 +296,7 @@ std::optional<int> CompileJobCache::initialize(CompilerInstance &Clang) {
   if (!CacheCompileJob)
     return std::nullopt;
 
-  std::tie(CAS, Cache) = Clang.createCASDatabases();
+  std::tie(CAS, Cache) = Clang.getOrCreateCASDatabases();
   if (!CAS || !Cache)
     return 1; // Exit with error!
 
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 238303ed963c3..cf8a970067144 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -296,6 +296,10 @@ void CompilerInstance::createVirtualFileSystem(
   DiagnosticsEngine Diags(DiagnosticIDs::create(), DiagOpts, DC,
                           /*ShouldOwnClient=*/false);
 
+  std::tie(CAS, ActionCache) =
+      getInvocation().getCASOpts().getOrCreateDatabases(
+          Diags, /*CreateEmptyCASOnFailure=*/false);
+
   VFS = createVFSFromCompilerInvocation(getInvocation(), Diags,
                                         std::move(BaseFS), CAS);
   // FIXME: Should this go into createVFSFromCompilerInvocation?
@@ -970,7 +974,7 @@ llvm::vfs::OutputBackend &CompilerInstance::getOrCreateOutputManager() {
 
 std::pair<std::shared_ptr<llvm::cas::ObjectStore>,
           std::shared_ptr<llvm::cas::ActionCache>>
-CompilerInstance::createCASDatabases() {
+CompilerInstance::getOrCreateCASDatabases() {
   // Create a new CAS databases from the CompilerInvocation. Future calls to
   // createFileManager() will use the same CAS.
   std::tie(CAS, ActionCache) =
@@ -982,13 +986,13 @@ CompilerInstance::createCASDatabases() {
 
 llvm::cas::ObjectStore &CompilerInstance::getOrCreateObjectStore() {
   if (!CAS)
-    createCASDatabases();
+    getOrCreateCASDatabases();
   return *CAS;
 }
 
 llvm::cas::ActionCache &CompilerInstance::getOrCreateActionCache() {
   if (!ActionCache)
-    createCASDatabases();
+    getOrCreateCASDatabases();
   return *ActionCache;
 }
 
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 5c11a86711d79..fff5458f78847 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1536,9 +1536,6 @@ createBaseFS(const FileSystemOptions &FSOpts, const FrontendOptions &FEOpts,
              const CASOptions &CASOpts, DiagnosticsEngine &Diags,
              IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
              std::shared_ptr<llvm::cas::ObjectStore> OverrideCAS) {
-  if (!OverrideCAS)
-    return BaseFS;
-
   if (FSOpts.CASFileSystemRootID.empty() && FEOpts.CASIncludeTreeID.empty())
     return BaseFS;
 
diff --git a/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp b/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp
index e27bd3e218017..c6900f9b84290 100644
--- a/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp
+++ b/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp
@@ -282,10 +282,11 @@ void dependencies::addReversePrefixMappingFileSystem(
   llvm::PrefixMapper ReverseMapper;
   ReverseMapper.addInverseRange(PrefixMapper.getMappings());
   ReverseMapper.sort();
-  std::unique_ptr<llvm::vfs::FileSystem> FS =
+  IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS =
       llvm::vfs::createPrefixMappingFileSystem(
           std::move(ReverseMapper), &ScanInstance.getVirtualFileSystem());
 
+  ScanInstance.setVirtualFileSystem(FS);
   ScanInstance.getFileManager().setVirtualFileSystem(std::move(FS));
 }
 
diff --git a/clang/test/CAS/output-path-error.c b/clang/test/CAS/output-path-error.c
index b217ba48402cf..a221f3bb29bf0 100644
--- a/clang/test/CAS/output-path-error.c
+++ b/clang/test/CAS/output-path-error.c
@@ -19,4 +19,4 @@
 // RUN: cat %t/output.txt | FileCheck %s --check-prefix=ERROR
 
 // CACHE-MISS: remark: compile job cache miss
-// ERROR: fatal error: CAS missing expected root-id
+// ERROR: fatal error: CAS filesystem cannot be initialized from root-id 'llvmcas://{{.*}}': cannot get reference to root FS