diff --git a/build/ffmpeg/ffmpeg.vcxproj b/build/ffmpeg/ffmpeg.vcxproj
index e6c54d187..bf207a0fe 100644
--- a/build/ffmpeg/ffmpeg.vcxproj
+++ b/build/ffmpeg/ffmpeg.vcxproj
@@ -91,7 +91,7 @@
     >
     <ExecShellScript
       Command="make"
-      Arguments="-j$(NUMBER_OF_PROCESSORS)"
+      Arguments="$(GmakeParallelBuild)"
       WorkingDirectory="$(AegisubObjectDir)"
       Configuration="@(ExecShellScript)"
       />
diff --git a/build/icu/icu.vcxproj b/build/icu/icu.vcxproj
index 5ac6755ee..f41c3569a 100644
--- a/build/icu/icu.vcxproj
+++ b/build/icu/icu.vcxproj
@@ -92,7 +92,7 @@
 
     <ExecShellScript
       Command="make"
-      Arguments="-j$(NUMBER_OF_PROCESSORS)"
+      Arguments="$(GmakeParallelBuild)"
       WorkingDirectory="$(AegisubObjectDir)"
       Configuration="@(ExecShellScript)"
       />
diff --git a/build/tasks.props b/build/tasks.props
index 0e4ea0846..06cda1f4b 100644
--- a/build/tasks.props
+++ b/build/tasks.props
@@ -19,6 +19,10 @@
     </ExecShellScript>
   </ItemGroup>
 
+  <PropertyGroup>
+    <GmakeParallelBuild Condition="'$(GmakeParallelBuild)'==''">-j$(NUMBER_OF_PROCESSORS)</GmakeParallelBuild>
+  </PropertyGroup>
+
   <UsingTask TaskName="ExecShellScript" AssemblyFile="$(AegisubBinaryDir)BuildTasks.dll" />
   <UsingTask TaskName="MsysPath" AssemblyFile="$(AegisubBinaryDir)BuildTasks.dll" />
   <UsingTask TaskName="UpdateFile" AssemblyFile="$(AegisubBinaryDir)BuildTasks.dll" />