diff --git a/modules/vstudio/tests/vc2010/test_files.lua b/modules/vstudio/tests/vc2010/test_files.lua
index b59888fbd..28e6e532e 100644
--- a/modules/vstudio/tests/vc2010/test_files.lua
+++ b/modules/vstudio/tests/vc2010/test_files.lua
@@ -657,6 +657,18 @@
 		]]
 	end
 
+	function suite.onCompileAsExt()
+		files { "hello.unknown_ext" }
+		filter "files:hello.unknown_ext"
+			compileas "C++"
+		prepare()
+		test.capture [[
+<ItemGroup>
+	<ClCompile Include="hello.unknown_ext">
+		<CompileAs>CompileAsCpp</CompileAs>
+		]]
+	end
+
 --
 -- Check handling of per-file cdialect.
 --
diff --git a/modules/vstudio/vs2010_vcxproj.lua b/modules/vstudio/vs2010_vcxproj.lua
index b31640325..e9ec8525e 100644
--- a/modules/vstudio/vs2010_vcxproj.lua
+++ b/modules/vstudio/vs2010_vcxproj.lua
@@ -1360,6 +1360,10 @@
 				if fcfg.buildaction then
 					return m.categories[fcfg.buildaction] or m.categories.None
 				end
+
+				if fcfg.compileas ~= nil and fcfg.compileas ~= "Default" then
+					return m.categories.ClCompile
+				end
 			end
 		end