diff --git a/r5dev/vproj/libimgui.vcxproj b/r5dev/vproj/libimgui.vcxproj
index 79f3c631..1ac287ed 100644
--- a/r5dev/vproj/libimgui.vcxproj
+++ b/r5dev/vproj/libimgui.vcxproj
@@ -174,7 +174,7 @@
       <SDLCheck>true</SDLCheck>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ConformanceMode>true</ConformanceMode>
-      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS %(AdditionalOptions)</AdditionalOptions>
+      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS /D BUILDING_LIBIMGUI %(AdditionalOptions)</AdditionalOptions>
       <LanguageStandard>stdcpp17</LanguageStandard>
     </ClCompile>
     <Link>
@@ -190,7 +190,7 @@
       <SDLCheck>true</SDLCheck>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ConformanceMode>true</ConformanceMode>
-      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS %(AdditionalOptions)</AdditionalOptions>
+      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS /D BUILDING_LIBIMGUI %(AdditionalOptions)</AdditionalOptions>
       <LanguageStandard>stdcpp17</LanguageStandard>
       <InlineFunctionExpansion>AnySuitable</InlineFunctionExpansion>
       <FavorSizeOrSpeed>Speed</FavorSizeOrSpeed>
@@ -210,7 +210,7 @@
       <SDLCheck>true</SDLCheck>
       <PreprocessorDefinitions>_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ConformanceMode>true</ConformanceMode>
-      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS %(AdditionalOptions)</AdditionalOptions>
+      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS /D BUILDING_LIBIMGUI %(AdditionalOptions)</AdditionalOptions>
       <LanguageStandard>stdcpp17</LanguageStandard>
     </ClCompile>
     <Link>
@@ -226,7 +226,7 @@
       <SDLCheck>true</SDLCheck>
       <PreprocessorDefinitions>NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ConformanceMode>true</ConformanceMode>
-      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS %(AdditionalOptions)</AdditionalOptions>
+      <AdditionalOptions>/D _CRT_SECURE_NO_WARNINGS /D BUILDING_LIBIMGUI %(AdditionalOptions)</AdditionalOptions>
       <LanguageStandard>stdcpp17</LanguageStandard>
       <OmitFramePointers>true</OmitFramePointers>
       <InlineFunctionExpansion>AnySuitable</InlineFunctionExpansion>