diff --git a/WatMakefile b/WatMakefile
index 55bc6b8..02205a7 100644
--- a/WatMakefile
+++ b/WatMakefile
@@ -1,7 +1,20 @@
 CC = wcc386 -bt=nt -q
 LD = wlink option quiet
 
-MW_CFLAGS = -bd -i=include -i=external/libz/include -d_MILSKO -d_MILSKO_BUILD -dUSE_GDI -dUSE_STB_IMAGE -dSTBI_NO_SIMD -dUSE_GDI_TEXT -dMW_OPENGL -dMW_DIRECTX8 -dMW_DIRECTX9
+!if [where d3d9.h >nul 2>nul]
+!if [for /f "delims=" %P in ('where d3d9.h 2^>nul') do @echo DX9_FLAGS = /DMW_DIRECTX9 /I"%~dpP">dx9flags.mk]
+!endif
+!else
+!if [echo DX9_FLAGS =>dx9flags.mk]
+!endif
+!endif
+!if exist("dx9flags.mk")
+!include "dx9flags.mk"
+!else
+DX9_FLAGS =
+!endif
+
+MW_CFLAGS = -bd -i=include -i=external/libz/include -d_MILSKO -d_MILSKO_BUILD -dUSE_GDI -dUSE_STB_IMAGE -dSTBI_NO_SIMD -dUSE_GDI_TEXT -dMW_OPENGL $(DX8_FLAGS) $(DX9_FLAGS)
 MW_LDFLAGS = system nt_dll
 EXE_CFLAGS = -i=include
 EXE_LDFLAGS = system nt
@@ -109,6 +122,7 @@ clean: .SYMBOLIC
 	%erase src/widget/window.obj
 	%erase src/Mw.dll
 	%erase src/Mw.lib
+	%erase dx9flags.mk
 	%erase examples/basic/box.obj
 	%erase examples/basic/calculator.obj
 	%erase examples/basic/checkbox.obj
diff --git a/tools/genmk.pl b/tools/genmk.pl
index a249e24..9f45add 100755
--- a/tools/genmk.pl
+++ b/tools/genmk.pl
@@ -154,8 +154,10 @@ sub generate {
         $needlibs = "${lib}clib3r.lib";
         $c_dllout = "option implib=src${dir}Mw.lib";
 
-        $dx8_flags = "${def}MW_DIRECTX8";
-        $dx9_flags = "${def}MW_DIRECTX9";
+        $dx8_flags = "\$(DX8_FLAGS)";
+        $dx8_block = dx8_detect_block();
+        $dx9_flags = "\$(DX9_FLAGS)";
+        $dx9_block = dx9_detect_block();
     }
 
     open(OUT, ">", $output);