diff --git a/build/tests/tests.vcxproj b/build/tests/tests.vcxproj
index aa1d92a71..1dbbfb1af 100644
--- a/build/tests/tests.vcxproj
+++ b/build/tests/tests.vcxproj
@@ -26,6 +26,7 @@
         $(SrcDir)support;
         %(AdditionalIncludeDirectories)
       </AdditionalIncludeDirectories>
+      <InputRelativeSourceDir>$(SrcDir)</InputRelativeSourceDir>
     </ClCompile>
     <Link>
       <AdditionalLibraryDirectories>$(AegisubLibraryDir);%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>