diff --git a/src/google/protobuf/generated_message_reflection.h b/src/google/protobuf/generated_message_reflection.h
index ed4e033..4f25d4b 100644
--- a/src/google/protobuf/generated_message_reflection.h
+++ b/src/google/protobuf/generated_message_reflection.h
@@ -635,6 +635,8 @@
 inline To dynamic_cast_if_available(From from) {
 #if defined(GOOGLE_PROTOBUF_NO_RTTI) || defined(__GXX_RTTI) || \
   (defined(_MSC_VER)&&!defined(_CPPRTTI))
+  // Avoid the compiler warning about unused variables.
+  (void)from;
   return NULL;
 #else
   return dynamic_cast<To>(from);
diff --git a/src/google/protobuf/wire_format.h b/src/google/protobuf/wire_format.h
index 941be75..5b41aad 100644
--- a/src/google/protobuf/wire_format.h
+++ b/src/google/protobuf/wire_format.h
@@ -326,6 +326,9 @@
 #ifdef GOOGLE_PROTOBUF_UTF8_VALIDATION_ENABLED
   WireFormatLite::VerifyUtf8String(
       data, size, static_cast<WireFormatLite::Operation>(op), field_name);
+#else
+  // Avoid the compiler warning about unused variables.
+  (void)data; (void)size; (void)op; (void)field_name;
 #endif
 }