--- /dev/null
+++ b/src/google/protobuf/arenastring.cc
@@ -0,0 +1,52 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/arenastring.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+::std::string* ArenaStringPtr::MutableNoArena(const ::std::string* default_value) {
+  if (ptr_ == default_value) {
+    CreateInstanceNoArena(default_value);
+  }
+  return ptr_;
+}
+
+void ArenaStringPtr::DestroyNoArena(const ::std::string* default_value) {
+  if (ptr_ != default_value) {
+    delete ptr_;
+  }
+}
+
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
--- a/src/google/protobuf/arenastring.h
+++ b/src/google/protobuf/arenastring.h
@@ -284,12 +284,7 @@ struct PROTOBUF_EXPORT ArenaStringPtr {
 
   inline const ::std::string& GetNoArena() const { return *ptr_; }
 
-  inline ::std::string* MutableNoArena(const ::std::string* default_value) {
-    if (ptr_ == default_value) {
-      CreateInstanceNoArena(default_value);
-    }
-    return ptr_;
-  }
+  ::std::string* MutableNoArena(const ::std::string* default_value);
 
   inline ::std::string* ReleaseNoArena(const ::std::string* default_value) {
     if (ptr_ == default_value) {
@@ -320,11 +315,7 @@ struct PROTOBUF_EXPORT ArenaStringPtr {
     }
   }
 
-  inline void DestroyNoArena(const ::std::string* default_value) {
-    if (ptr_ != default_value) {
-      delete ptr_;
-    }
-  }
+  void DestroyNoArena(const ::std::string* default_value);
 
   inline void ClearToEmptyNoArena(const ::std::string* default_value) {
     if (ptr_ == default_value) {