diff --git a/clang/include/clang/AST/ASTImporter.h b/clang/include/clang/AST/ASTImporter.h
--- a/clang/include/clang/AST/ASTImporter.h
+++ b/clang/include/clang/AST/ASTImporter.h
@@ -87,8 +87,8 @@
     using NonEquivalentDeclSet = llvm::DenseSet<std::pair<Decl *, Decl *>>;
     using ImportedCXXBaseSpecifierMap =
         llvm::DenseMap<const CXXBaseSpecifier *, CXXBaseSpecifier *>;
-    using FileIDImportHandlerType = std::function<void(
-        FileID /*ToID*/, FileID /*FromID*/, ASTImporter & /*Importer*/)>;
+    using FileIDImportHandlerType =
+        std::function<void(FileID /*ToID*/, FileID /*FromID*/)>;
 
     // An ImportPath is the list of the AST nodes which we visit during an
     // Import call.
@@ -317,7 +317,7 @@
     /// Set a callback function for FileID import handling.
     /// The function is invoked when a FileID is imported from the From context.
     /// The imported FileID in the To context and the original FileID in the
-    /// From context, and the ASTImporter itself are passed to it.
+    /// From context is passed to it.
     void setFileIDImportHandler(FileIDImportHandlerType H) {
       FileIDImportHandler = H;
     }
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -8423,7 +8423,7 @@
   ImportedFileIDs[FromID] = ToID;
 
   if (FileIDImportHandler)
-    FileIDImportHandler(ToID, FromID, *this);
+    FileIDImportHandler(ToID, FromID);
 
   return ToID;
 }
diff --git a/clang/lib/CrossTU/CrossTranslationUnit.cpp b/clang/lib/CrossTU/CrossTranslationUnit.cpp
--- a/clang/lib/CrossTU/CrossTranslationUnit.cpp
+++ b/clang/lib/CrossTU/CrossTranslationUnit.cpp
@@ -472,12 +472,11 @@
   ASTImporter *NewImporter = new ASTImporter(
       Context, Context.getSourceManager().getFileManager(), From,
       From.getSourceManager().getFileManager(), false, ImporterSharedSt);
-  NewImporter->setFileIDImportHandler(
-      [this, Unit](FileID ToID, FileID FromID, ASTImporter &Importer) {
-        assert(ImportedFileIDs.find(ToID) == ImportedFileIDs.end() &&
-               "FileID already imported, should not happen.");
-        ImportedFileIDs[ToID] = std::make_pair(FromID, Unit);
-      });
+  NewImporter->setFileIDImportHandler([this, Unit](FileID ToID, FileID FromID) {
+    assert(ImportedFileIDs.find(ToID) == ImportedFileIDs.end() &&
+           "FileID already imported, should not happen.");
+    ImportedFileIDs[ToID] = std::make_pair(FromID, Unit);
+  });
   ASTUnitImporterMap[From.getTranslationUnitDecl()].reset(NewImporter);
   return *NewImporter;
 }