diff --git a/src/google/protobuf/compiler/objectivec/file.cc b/src/google/protobuf/compiler/objectivec/file.cc
index c2093ddda3..3ede6ee965 100644
--- a/src/google/protobuf/compiler/objectivec/file.cc
+++ b/src/google/protobuf/compiler/objectivec/file.cc
@@ -221,7 +221,7 @@ FileGenerator::FileGenerator(const FileDescriptor* file,
                              CommonState& common_state)
     : file_(file),
       generation_options_(generation_options),
-      common_state_(common_state),
+      common_state_(&common_state),
       root_class_name_(FileClassName(file)),
       is_bundled_proto_(IsProtobufLibraryBundledProtoFile(file)) {
   for (int i = 0; i < file_->enum_type_count(); i++) {
@@ -241,7 +241,7 @@ FileGenerator::FileGenerator(const FileDescriptor* file,
   }
 }
 
-void FileGenerator::GenerateHeader(io::Printer* printer) {
+void FileGenerator::GenerateHeader(io::Printer* printer) const {
   std::vector<std::string> headers;
   // Generated files bundled with the library get minimal imports, everything
   // else gets the wrapper so everything is usable.
@@ -393,7 +393,7 @@ void FileGenerator::GenerateHeader(io::Printer* printer) {
   // clang-format on
 }
 
-void FileGenerator::GenerateSource(io::Printer* printer) {
+void FileGenerator::GenerateSource(io::Printer* printer) const {
   // #import the runtime support.
   std::vector<std::string> headers;
   headers.push_back("GPBProtocolBuffers_RuntimeSupport.h");
@@ -410,7 +410,7 @@ void FileGenerator::GenerateSource(io::Printer* printer) {
   }
 
   std::vector<const FileDescriptor*> deps_with_extensions =
-      common_state_.CollectMinimalFileDepsContainingExtensions(file_);
+      common_state_->CollectMinimalFileDepsContainingExtensions(file_);
 
   // The bundled protos (WKTs) don't use of forward declarations.
   bool headers_use_forward_declarations =
diff --git a/src/google/protobuf/compiler/objectivec/file.h b/src/google/protobuf/compiler/objectivec/file.h
index 3946a05cf3..b62a8562e8 100644
--- a/src/google/protobuf/compiler/objectivec/file.h
+++ b/src/google/protobuf/compiler/objectivec/file.h
@@ -80,15 +80,15 @@ class FileGenerator {
   FileGenerator(const FileGenerator&) = delete;
   FileGenerator& operator=(const FileGenerator&) = delete;
 
-  void GenerateSource(io::Printer* printer);
-  void GenerateHeader(io::Printer* printer);
+  void GenerateSource(io::Printer* printer) const;
+  void GenerateHeader(io::Printer* printer) const;
 
  private:
   const FileDescriptor* file_;
   const GenerationOptions& generation_options_;
-  CommonState& common_state_;
-  std::string root_class_name_;
-  bool is_bundled_proto_;
+  mutable CommonState* common_state_;
+  const std::string root_class_name_;
+  const bool is_bundled_proto_;
 
   std::vector<std::unique_ptr<EnumGenerator>> enum_generators_;
   std::vector<std::unique_ptr<MessageGenerator>> message_generators_;
diff --git a/src/google/protobuf/compiler/objectivec/oneof.cc b/src/google/protobuf/compiler/objectivec/oneof.cc
index 4dfaf98171..99b2149379 100644
--- a/src/google/protobuf/compiler/objectivec/oneof.cc
+++ b/src/google/protobuf/compiler/objectivec/oneof.cc
@@ -67,11 +67,11 @@ void OneofGenerator::SetOneofIndexBase(int index_base) {
   variables_["index"] = absl::StrCat(-index);
 }
 
-void OneofGenerator::GenerateCaseEnum(io::Printer* printer) {
+void OneofGenerator::GenerateCaseEnum(io::Printer* printer) const {
   printer->Print(variables_, "typedef GPB_ENUM($enum_name$) {\n");
   printer->Indent();
   printer->Print(variables_, "$enum_name$_GPBUnsetOneOfCase = 0,\n");
-  std::string enum_name = variables_["enum_name"];
+  std::string enum_name = variables_.find("enum_name")->second;
   for (int j = 0; j < descriptor_->field_count(); j++) {
     const FieldDescriptor* field = descriptor_->field(j);
     std::string field_name = FieldNameCapitalized(field);
@@ -88,7 +88,7 @@ void OneofGenerator::GenerateCaseEnum(io::Printer* printer) {
 }
 
 void OneofGenerator::GeneratePublicCasePropertyDeclaration(
-    io::Printer* printer) {
+    io::Printer* printer) const {
   // clang-format off
   printer->Print(
       variables_,
@@ -98,7 +98,8 @@ void OneofGenerator::GeneratePublicCasePropertyDeclaration(
   // clang-format on
 }
 
-void OneofGenerator::GenerateClearFunctionDeclaration(io::Printer* printer) {
+void OneofGenerator::GenerateClearFunctionDeclaration(
+    io::Printer* printer) const {
   // clang-format off
   printer->Print(
       variables_,
@@ -109,11 +110,13 @@ void OneofGenerator::GenerateClearFunctionDeclaration(io::Printer* printer) {
   // clang-format on
 }
 
-void OneofGenerator::GeneratePropertyImplementation(io::Printer* printer) {
+void OneofGenerator::GeneratePropertyImplementation(
+    io::Printer* printer) const {
   printer->Print(variables_, "@dynamic $name$OneOfCase;\n");
 }
 
-void OneofGenerator::GenerateClearFunctionImplementation(io::Printer* printer) {
+void OneofGenerator::GenerateClearFunctionImplementation(
+    io::Printer* printer) const {
   // clang-format off
   printer->Print(
       variables_,
diff --git a/src/google/protobuf/compiler/objectivec/oneof.h b/src/google/protobuf/compiler/objectivec/oneof.h
index d9a23f902c..398a9623dd 100644
--- a/src/google/protobuf/compiler/objectivec/oneof.h
+++ b/src/google/protobuf/compiler/objectivec/oneof.h
@@ -53,13 +53,13 @@ class OneofGenerator {
 
   void SetOneofIndexBase(int index_base);
 
-  void GenerateCaseEnum(io::Printer* printer);
+  void GenerateCaseEnum(io::Printer* printer) const;
 
-  void GeneratePublicCasePropertyDeclaration(io::Printer* printer);
-  void GenerateClearFunctionDeclaration(io::Printer* printer);
+  void GeneratePublicCasePropertyDeclaration(io::Printer* printer) const;
+  void GenerateClearFunctionDeclaration(io::Printer* printer) const;
 
-  void GeneratePropertyImplementation(io::Printer* printer);
-  void GenerateClearFunctionImplementation(io::Printer* printer);
+  void GeneratePropertyImplementation(io::Printer* printer) const;
+  void GenerateClearFunctionImplementation(io::Printer* printer) const;
 
   std::string DescriptorName() const;
   std::string HasIndexAsString() const;