diff --git a/src/google/protobuf/compiler/cpp/cpp_helpers.h b/src/google/protobuf/compiler/cpp/cpp_helpers.h
index 5fa019d216bc..b53c46f86fbc 100644
--- a/src/google/protobuf/compiler/cpp/cpp_helpers.h
+++ b/src/google/protobuf/compiler/cpp/cpp_helpers.h
@@ -59,7 +59,7 @@ namespace protobuf {
 namespace compiler {
 namespace cpp {
 
-inline std::string ProtobufNamespace(const Options& options) {
+inline std::string ProtobufNamespace(const Options& /* options */) {
   return "PROTOBUF_NAMESPACE_ID";
 }
 
@@ -67,12 +67,12 @@ inline std::string MacroPrefix(const Options& options) {
   return options.opensource_runtime ? "GOOGLE_PROTOBUF" : "GOOGLE_PROTOBUF";
 }
 
-inline std::string DeprecatedAttribute(const Options& options,
+inline std::string DeprecatedAttribute(const Options& /* options */,
                                        const FieldDescriptor* d) {
   return d->options().deprecated() ? "PROTOBUF_DEPRECATED " : "";
 }
 
-inline std::string DeprecatedAttribute(const Options& options,
+inline std::string DeprecatedAttribute(const Options& /* options */,
                                        const EnumValueDescriptor* d) {
   return d->options().deprecated() ? "PROTOBUF_DEPRECATED_ENUM " : "";
 }
@@ -345,7 +345,7 @@ inline bool IsLazy(const FieldDescriptor* field, const Options& options) {
          !options.opensource_runtime;
 }
 
-inline bool IsFieldUsed(const FieldDescriptor* field, const Options& options) {
+inline bool IsFieldUsed(const FieldDescriptor* /* field */, const Options& /* options */) {
   return true;
 }
 
diff --git a/src/google/protobuf/compiler/importer.h b/src/google/protobuf/compiler/importer.h
index db4a876c5bb6..6cdae8a12d26 100644
--- a/src/google/protobuf/compiler/importer.h
+++ b/src/google/protobuf/compiler/importer.h
@@ -202,8 +202,8 @@ class PROTOBUF_EXPORT MultiFileErrorCollector {
   virtual void AddError(const std::string& filename, int line, int column,
                         const std::string& message) = 0;
 
-  virtual void AddWarning(const std::string& filename, int line, int column,
-                          const std::string& message) {}
+  virtual void AddWarning(const std::string& /* filename */, int /* line */, int /* column */,
+                          const std::string& /* message */) {}
 
  private:
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MultiFileErrorCollector);
diff --git a/src/google/protobuf/io/printer.h b/src/google/protobuf/io/printer.h
index 64336ebcefed..904b81818bb0 100644
--- a/src/google/protobuf/io/printer.h
+++ b/src/google/protobuf/io/printer.h
@@ -65,7 +65,7 @@ class PROTOBUF_EXPORT AnnotationCollector {
 
   // TODO(gerbens) I don't see why we need virtuals here. Just a vector of
   // range, payload pairs stored in a context should suffice.
-  virtual void AddAnnotationNew(Annotation& a) {}
+  virtual void AddAnnotationNew(Annotation& /* a */) {}
 
   virtual ~AnnotationCollector() {}
 };
diff --git a/src/google/protobuf/io/tokenizer.h b/src/google/protobuf/io/tokenizer.h
index 551516ea3970..3be00f11eacc 100644
--- a/src/google/protobuf/io/tokenizer.h
+++ b/src/google/protobuf/io/tokenizer.h
@@ -78,8 +78,8 @@ class PROTOBUF_EXPORT ErrorCollector {
   // Indicates that there was a warning in the input at the given line and
   // column numbers.  The numbers are zero-based, so you may want to add
   // 1 to each before printing them.
-  virtual void AddWarning(int line, ColumnNumber column,
-                          const std::string& message) {}
+  virtual void AddWarning(int /* line */, ColumnNumber /* column */,
+                          const std::string& /* message */) {}
 
  private:
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ErrorCollector);