diff --git a/src/sbbs3/sexyz.vcxproj b/src/sbbs3/sexyz.vcxproj
index 68a0a5161f16fd7408748d04285b0ed98c554ec5..ac8759243018feaac7089a3c0b98554d7ce54147 100644
--- a/src/sbbs3/sexyz.vcxproj
+++ b/src/sbbs3/sexyz.vcxproj
@@ -66,7 +66,7 @@
     <ClCompile>
       <Optimization>Disabled</Optimization>
       <AdditionalIncludeDirectories>%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>_DEBUG;WIN32;_CONSOLE;SBBS_EXPORTS;RINGBUF_SEM;RINGBUF_EVENT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>_DEBUG;WIN32;_CONSOLE;SBBS_EXPORTS;RINGBUF_SEM;RINGBUF_EVENT;RINGBUF_MUTEX;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
       <PrecompiledHeaderOutputFile>.\msvc.win32.debug\sexyz/sexyz.pch</PrecompiledHeaderOutputFile>
@@ -110,7 +110,7 @@
       <Optimization>MaxSpeed</Optimization>
       <InlineFunctionExpansion>OnlyExplicitInline</InlineFunctionExpansion>
       <AdditionalIncludeDirectories>%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>NDEBUG;WIN32;_CONSOLE;SBBS_EXPORTS;RINGBUF_SEM;RINGBUF_EVENT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>NDEBUG;WIN32;_CONSOLE;SBBS_EXPORTS;RINGBUF_SEM;RINGBUF_EVENT;RINGBUF_MUTEX;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <StringPooling>true</StringPooling>
       <RuntimeLibrary>MultiThreadedDLL</RuntimeLibrary>
       <FunctionLevelLinking>true</FunctionLevelLinking>