diff --git a/windows/vcpp2010/examples/wsperf/wsperf.vcxproj b/windows/vcpp2010/examples/wsperf/wsperf.vcxproj
index 9886234e41..dce6ac4ef4 100644
--- a/windows/vcpp2010/examples/wsperf/wsperf.vcxproj
+++ b/windows/vcpp2010/examples/wsperf/wsperf.vcxproj
@@ -65,7 +65,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>_WEBSOCKETPP_CPP11_FRIEND_;WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(BOOSTROOT);..;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
       <BufferSecurityCheck>false</BufferSecurityCheck>