diff --git a/.github/workflows/os2.yml b/.github/workflows/os2.yml
deleted file mode 100644
index 2ae10643b..000000000
--- a/.github/workflows/os2.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-name: Build (OS/2)
-
-on: [push, pull_request]
-
-jobs:
-  os2:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - uses: open-watcom/setup-watcom@v0
-      - name: Build SDL2
-        run: |
-          wmake -f Makefile.os2
-      - name: Build tests
-        run: |
-          cd test && wmake -f Makefile.os2
-          cd ..
-      - name: distclean
-        run: |
-          wmake -f Makefile.os2 distclean
-          cd test && wmake -f Makefile.os2 distclean
-          cd ..
diff --git a/.github/workflows/watcom.yml b/.github/workflows/watcom.yml
new file mode 100644
index 000000000..4650246c6
--- /dev/null
+++ b/.github/workflows/watcom.yml
@@ -0,0 +1,30 @@
+name: Build (OpenWatcom)
+
+on: [push, pull_request]
+
+jobs:
+  os2:
+    name: ${{ matrix.platform.name }}
+    runs-on: windows-latest
+
+    strategy:
+      matrix:
+        platform:
+        - { name: Windows, makefile: Makefile.w32 }
+        - { name: OS/2,    makefile: Makefile.os2 }
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: open-watcom/setup-watcom@v0
+      - name: Build SDL2
+        run: |
+          wmake -f ${{ matrix.platform.makefile }}
+      - name: Build tests
+        run: |
+          cd test && wmake -f ${{ matrix.platform.makefile }}
+          cd ..
+      - name: distclean
+        run: |
+          wmake -f ${{ matrix.platform.makefile }} distclean
+          cd test && wmake -f ${{ matrix.platform.makefile }} distclean
+          cd ..
diff --git a/.gitignore b/.gitignore
index fd27cb76a..1f5e7249f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,6 +22,7 @@ buildbot
 *.exe
 *.o
 *.obj
+*.res
 *.lib
 *.a
 *.la
diff --git a/Makefile.w32 b/Makefile.w32
new file mode 100644
index 000000000..780593fd3
--- /dev/null
+++ b/Makefile.w32
@@ -0,0 +1,219 @@
+# Open Watcom makefile to build SDL2.dll for Win32
+# wmake -f Makefile.w32
+
+LIBNAME = SDL2
+MAJOR_VERSION = 2
+MINOR_VERSION = 23
+MICRO_VERSION = 0
+VERSION = $(MAJOR_VERSION).$(MINOR_VERSION).$(MICRO_VERSION)
+DESCRIPTION = Simple DirectMedia Layer 2
+
+LIBHOME = .
+DLLFILE = $(LIBHOME)/$(LIBNAME).dll
+LIBFILE = $(LIBHOME)/$(LIBNAME).lib
+LNKFILE = $(LIBNAME).lnk
+
+INCPATH = -I"$(%WATCOM)/h/nt" -I"$(%WATCOM)/h/nt/directx" -I"$(%WATCOM)/h"
+INCPATH+= -Iinclude
+INCPATH+= -I"src/video/khronos"
+
+TLIB = SDL2test.lib
+LIBS = user32.lib gdi32.lib winmm.lib imm32.lib ole32.lib oleaut32.lib shell32.lib setupapi.lib version.lib uuid.lib dxguid.lib
+
+CFLAGS = -bt=nt -d0 -q -bm -5s -fp5 -fpi87 -sg -oeatxhn -ei
+# max warnings:
+CFLAGS+= -wx
+# newer OpenWatcom versions enable W303 by default
+CFLAGS+= -wcd=303
+# the include paths :
+CFLAGS+= $(INCPATH)
+CFLAGS_STATIC=$(CFLAGS)
+# building dll:
+CFLAGS_DLL =$(CFLAGS)
+CFLAGS_DLL+= -bd
+# building SDL itself (for DECLSPEC):
+CFLAGS_DLL+= -DDLL_EXPORT
+
+CFLAGS_DLL+= -DSDL_BUILD_MAJOR_VERSION=$(MAJOR_VERSION)
+CFLAGS_DLL+= -DSDL_BUILD_MINOR_VERSION=$(MINOR_VERSION)
+CFLAGS_DLL+= -DSDL_BUILD_MICRO_VERSION=$(MICRO_VERSION)
+
+RCFLAGS = -q -r -bt=nt $(INCPATH)
+
+SRCS = SDL.c SDL_assert.c SDL_error.c SDL_log.c SDL_dataqueue.c SDL_hints.c SDL_list.c
+SRCS+= SDL_getenv.c SDL_iconv.c SDL_malloc.c SDL_qsort.c SDL_stdlib.c SDL_string.c SDL_strtokr.c SDL_crc32.c
+SRCS+= SDL_cpuinfo.c SDL_atomic.c SDL_spinlock.c SDL_thread.c SDL_timer.c
+SRCS+= SDL_rwops.c SDL_power.c
+SRCS+= SDL_audio.c SDL_audiocvt.c SDL_audiodev.c SDL_audiotypecvt.c SDL_mixer.c SDL_wave.c
+SRCS+= SDL_events.c SDL_quit.c SDL_keyboard.c SDL_mouse.c SDL_windowevents.c &
+       SDL_clipboardevents.c SDL_dropevents.c SDL_displayevents.c SDL_gesture.c &
+       SDL_sensor.c SDL_touch.c
+SRCS+= SDL_haptic.c SDL_hidapi.c SDL_gamecontroller.c SDL_joystick.c
+SRCS+= SDL_render.c yuv_rgb.c SDL_yuv.c SDL_yuv_sw.c SDL_blendfillrect.c &
+       SDL_blendline.c SDL_blendpoint.c SDL_drawline.c SDL_drawpoint.c &
+       SDL_render_sw.c SDL_rotate.c SDL_triangle.c
+SRCS+= SDL_blit.c SDL_blit_0.c SDL_blit_1.c SDL_blit_A.c SDL_blit_auto.c &
+       SDL_blit_copy.c SDL_blit_N.c SDL_blit_slow.c SDL_fillrect.c SDL_bmp.c &
+       SDL_pixels.c SDL_rect.c SDL_RLEaccel.c SDL_shape.c SDL_stretch.c &
+       SDL_surface.c SDL_video.c SDL_clipboard.c SDL_vulkan_utils.c SDL_egl.c
+
+SRCS+= e_atan2.c e_exp.c e_fmod.c e_log10.c e_log.c e_pow.c e_rem_pio2.c e_sqrt.c &
+       k_cos.c k_rem_pio2.c k_sin.c k_tan.c &
+       s_atan.c s_copysign.c s_cos.c s_fabs.c s_floor.c s_scalbn.c s_sin.c s_tan.c
+
+SRCS+= SDL_syscond.c SDL_sysmutex.c SDL_syssem.c SDL_systhread.c SDL_systls.c
+SRCS+= SDL_systimer.c
+SRCS+= SDL_sysloadso.c
+SRCS+= SDL_sysfilesystem.c
+SRCS+= SDL_syshaptic.c SDL_sysjoystick.c SDL_virtualjoystick.c
+SRCS+= SDL_hidapijoystick.c SDL_hidapi_rumble.c SDL_hidapi_gamecube.c SDL_hidapi_luna.c SDL_hidapi_ps4.c SDL_hidapi_ps5.c SDL_hidapi_stadia.c SDL_hidapi_switch.c SDL_hidapi_xbox360.c SDL_hidapi_xbox360w.c SDL_hidapi_xboxone.c SDL_hidapi_steam.c
+SRCS+= SDL_dummyaudio.c SDL_diskaudio.c
+SRCS+= SDL_nullvideo.c SDL_nullframebuffer.c SDL_nullevents.c
+SRCS+= SDL_dummysensor.c
+SRCS+= SDL_locale.c SDL_syslocale.c
+SRCS+= SDL_url.c SDL_sysurl.c
+
+SRCS+= SDL_winmm.c SDL_directsound.c SDL_wasapi.c SDL_wasapi_win32.c
+SRCS+= SDL_hid.c SDL_windows.c SDL_xinput.c
+SRCS+= SDL_dinputhaptic.c SDL_windowshaptic.c SDL_xinputhaptic.c
+SRCS+= SDL_dinputjoystick.c SDL_rawinputjoystick.c SDL_windowsjoystick.c SDL_windows_gaming_input.c SDL_xinputjoystick.c
+SRCS+= SDL_syspower.c
+SRCS+= SDL_d3dmath.c
+SRCS+= SDL_render_d3d.c SDL_shaders_d3d.c
+SRCS+= SDL_render_d3d11.c SDL_shaders_d3d11.c
+SRCS+= SDL_render_gl.c SDL_shaders_gl.c
+SRCS+= SDL_render_gles2.c SDL_shaders_gles2.c
+SRCS+= SDL_windowssensor.c
+SRCS+= SDL_syscond_cv.c
+SRCS+= SDL_windowsclipboard.c SDL_windowsevents.c SDL_windowsframebuffer.c SDL_windowskeyboard.c SDL_windowsmessagebox.c SDL_windowsmodes.c SDL_windowsmouse.c SDL_windowsopengl.c SDL_windowsopengles.c SDL_windowsshape.c SDL_windowsvideo.c SDL_windowsvulkan.c SDL_windowswindow.c
+
+SRCS+= SDL_dynapi.c
+
+RCSRCS+= version.rc
+
+OBJS = $(SRCS:.c=.obj)
+RCOBJS= $(RCSRCS:.rc=.res)
+
+.extensions:
+.extensions: .lib .dll .obj .res .c .rc .asm
+
+.c: ./src/libm;
+.c: ./src;./src/dynapi;./src/audio;./src/cpuinfo;./src/events;./src/file;./src/haptic;./src/joystick;./src/power;./src/render;./src/render/software;./src/sensor;./src/stdlib;./src/thread;./src/timer;./src/video;./src/video/yuv2rgb;./src/atomic;./src/audio/disk;
+.c: ./src/haptic/dummy;./src/joystick/dummy;./src/joystick/virtual;./src/audio/dummy;./src/video/dummy;./src/sensor/dummy;
+.c: ./src/core/windows;./src/audio/winmm;./src/audio/directsound;./src/audio/wasapi;./src/loadso/windows;./src/filesystem/windows;./src/haptic/windows;./src/joystick/windows;./src/sensor/windows;./src/thread/windows;./src/timer/windows;./src/video/windows;
+.c: ./src/locale/;./src/locale/windows;./src/misc;./src/misc/windows;./src/power/windows;./src/joystick/hidapi;./src/hidapi;./src/render/direct3d;./src/render/direct3d11;./src/render/opengl;./src/render/opengles2
+.rc: ./src/main/windows
+
+all: $(DLLFILE) $(LIBFILE) $(TLIB) .symbolic
+
+build_dll: .symbolic
+    @echo * Compiling dll objects
+
+$(DLLFILE): build_dll $(OBJS) $(MOBJS) $(RCOBJS) $(LNKFILE)
+    @echo * Linking: $@
+    wlink @$(LNKFILE)
+    wrc $(RCOBJS) $^@
+
+$(LIBFILE): $(DLLFILE)
+    @echo * Creating LIB file: $@
+    wlib -q -b -n -c -pa -s -t -zld -ii -io $* $(DLLFILE)
+
+.c.obj:
+    wcc386 $(CFLAGS_DLL) -fo=$^@ $<
+
+.rc.res:
+    wrc $(RCFLAGS) -fo=$^@ $<
+
+SDL_syscond.obj: "src/thread/generic/SDL_syscond.c"
+    wcc386 $(CFLAGS_DLL) -fo=$^@ $<
+SDL_cpuinfo.obj: SDL_cpuinfo.c
+    wcc386 $(CFLAGS_DLL) -wcd=200 -fo=$^@ $<
+SDL_wave.obj: SDL_wave.c
+    wcc386 $(CFLAGS_DLL) -wcd=124 -fo=$^@ $<
+SDL_blendfillrect.obj: SDL_blendfillrect.c
+    wcc386 $(CFLAGS_DLL) -wcd=200 -fo=$^@ $<
+SDL_blendline.obj: SDL_blendline.c
+    wcc386 $(CFLAGS_DLL) -wcd=200 -fo=$^@ $<
+SDL_blendpoint.obj: SDL_blendpoint.c
+    wcc386 $(CFLAGS_DLL) -wcd=200 -fo=$^@ $<
+SDL_RLEaccel.obj: SDL_RLEaccel.c
+    wcc386 $(CFLAGS_DLL) -wcd=201 -fo=$^@ $<
+# c99 mode needed because of structs with flexible array members in libusb.h
+SDL_hidapi.obj: SDL_hidapi.c
+    wcc386 $(CFLAGS_DLL) -za99 -fo=$^@ $<
+
+# SDL2test
+TSRCS = SDL_test_assert.c SDL_test_common.c SDL_test_compare.c &
+        SDL_test_crc32.c SDL_test_font.c SDL_test_fuzzer.c SDL_test_harness.c &
+        SDL_test_imageBlit.c SDL_test_imageBlitBlend.c SDL_test_imageFace.c &
+        SDL_test_imagePrimitives.c SDL_test_imagePrimitivesBlend.c &
+        SDL_test_log.c SDL_test_md5.c SDL_test_random.c SDL_test_memory.c
+TOBJS= $(TSRCS:.c=.obj)
+
+.c: ./src/test;
+SDL_test_assert.obj: SDL_test_assert.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_common.obj: SDL_test_common.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_compare.obj: SDL_test_compare.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_crc32.obj: SDL_test_crc32.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_font.obj: SDL_test_font.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_fuzzer.obj: SDL_test_fuzzer.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_harness.obj: SDL_test_harness.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_imageBlit.obj: SDL_test_imageBlit.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_imageBlitBlend.obj: SDL_test_imageBlitBlend.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_imageFace.obj: SDL_test_imageFace.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_imagePrimitives.obj: SDL_test_imagePrimitives.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_imagePrimitivesBlend.obj: SDL_test_imagePrimitivesBlend.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_log.obj: SDL_test_log.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_md5.obj: SDL_test_md5.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_random.obj: SDL_test_random.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+SDL_test_memory.obj: SDL_test_memory.c
+    wcc386 $(CFLAGS_STATIC) -fo=$^@ $<
+
+build_tlib: .symbolic
+    @echo * Compiling testlib objects
+$(TLIB): build_tlib $(TOBJS)
+    @echo * Creating: $@
+    wlib -q -b -n -c -pa -s -t -zld -ii -io $@ $(TOBJS)
+
+$(LNKFILE): Makefile.w32
+    @echo * Creating linker file: $@
+    @%create $@
+    @%append $@ SYSTEM nt_dll INITINSTANCE TERMINSTANCE
+    @%append $@ NAME $(DLLFILE)
+    @for %i in ($(OBJS)) do @%append $@ FILE %i
+    @for %i in ($(LIBS)) do @%append $@ LIB %i
+    @%append $@ OPTION QUIET
+    @%append $@ OPTION IMPF=$(LIBHOME)/$^&.exp
+    @%append $@ OPTION MAP=$(LIBHOME)/$^&.map
+    @%append $@ OPTION DESCRIPTION '@$#libsdl org:$(VERSION)$#@$(DESCRIPTION)'
+    @%append $@ OPTION ELIMINATE
+    @%append $@ OPTION OSNAME='Windows NT'
+    @%append $@ OPTION SHOWDEAD
+
+clean: .SYMBOLIC
+    @echo * Clean: $(LIBNAME)
+    @if exist *.obj rm *.obj
+    @if exist *.err rm *.err
+    @if exist $(LNKFILE) rm $(LNKFILE)
+
+distclean: .SYMBOLIC clean
+    @if exist $(LIBHOME)/*.exp rm $(LIBHOME)/*.exp
+    @if exist $(LIBHOME)/*.map rm $(LIBHOME)/*.map
+    @if exist $(LIBFILE) rm $(LIBFILE)
+    @if exist $(DLLFILE) rm $(DLLFILE)
+    @if exist $(TLIB) rm $(TLIB)
diff --git a/include/SDL_config_windows.h b/include/SDL_config_windows.h
index 90f5ddc06..81fde40c8 100644
--- a/include/SDL_config_windows.h
+++ b/include/SDL_config_windows.h
@@ -97,6 +97,7 @@ typedef unsigned int uintptr_t;
 #define HAVE_DDRAW_H 1
 #define HAVE_DINPUT_H 1
 #define HAVE_DSOUND_H 1
+#ifndef __WATCOMC__
 #define HAVE_DXGI_H 1
 #define HAVE_XINPUT_H 1
 #if defined(_WIN32_MAXVER) && _WIN32_MAXVER >= 0x0A00  /* Windows 10 SDK */
@@ -110,6 +111,7 @@ typedef unsigned int uintptr_t;
 #define HAVE_AUDIOCLIENT_H 1
 #define HAVE_TPCSHRD_H 1
 #define HAVE_SENSORSAPI_H 1
+#endif
 #if (defined(_M_IX86) || defined(_M_X64) || defined(_M_AMD64)) && (defined(_MSC_VER) && _MSC_VER >= 1600)
 #define HAVE_IMMINTRIN_H 1
 #elif defined(__has_include) && (defined(__i386__) || defined(__x86_64))
@@ -136,8 +138,11 @@ typedef unsigned int uintptr_t;
 #define HAVE_REALLOC 1
 #define HAVE_FREE 1
 #define HAVE_ALLOCA 1
+/* OpenWatcom requires specific calling conventions for qsort and bsearch */
+#ifndef __WATCOMC__
 #define HAVE_QSORT 1
 #define HAVE_BSEARCH 1
+#endif
 #define HAVE_ABS 1
 #define HAVE_MEMSET 1
 #define HAVE_MEMCPY 1
@@ -168,37 +173,40 @@ typedef unsigned int uintptr_t;
 #define HAVE__WCSNICMP 1
 #define HAVE__WCSDUP 1
 #define HAVE_ACOS   1
-#define HAVE_ACOSF  1
 #define HAVE_ASIN   1
-#define HAVE_ASINF  1
 #define HAVE_ATAN   1
-#define HAVE_ATANF  1
 #define HAVE_ATAN2  1
+#define HAVE_CEIL   1
+#define HAVE_COS    1
+#define HAVE_EXP    1
+#define HAVE_FABS   1
+#define HAVE_FLOOR  1
+#define HAVE_FMOD   1
+#define HAVE_LOG    1
+#define HAVE_LOG10  1
+#define HAVE_POW    1
+#define HAVE_SIN    1
+#define HAVE_SQRT   1
+#define HAVE_TAN    1
+#ifndef __WATCOMC__
+#define HAVE_ACOSF  1
+#define HAVE_ASINF  1
+#define HAVE_ATANF  1
 #define HAVE_ATAN2F 1
 #define HAVE_CEILF  1
 #define HAVE__COPYSIGN 1
-#define HAVE_COS    1
 #define HAVE_COSF   1
-#define HAVE_EXP    1
 #define HAVE_EXPF   1
-#define HAVE_FABS   1
 #define HAVE_FABSF  1
-#define HAVE_FLOOR  1
 #define HAVE_FLOORF 1
-#define HAVE_FMOD   1
 #define HAVE_FMODF  1
-#define HAVE_LOG    1
 #define HAVE_LOGF   1
-#define HAVE_LOG10  1
 #define HAVE_LOG10F 1
-#define HAVE_POW    1
 #define HAVE_POWF   1
-#define HAVE_SIN    1
 #define HAVE_SINF   1
-#define HAVE_SQRT   1
 #define HAVE_SQRTF  1
-#define HAVE_TAN    1
 #define HAVE_TANF   1
+#endif
 #if defined(_MSC_VER)
 /* These functions were added with the VC++ 2013 C runtime library */
 #if _MSC_VER >= 1800
@@ -218,8 +226,18 @@ typedef unsigned int uintptr_t;
 #if _MSC_VER >= 1400
 #define HAVE__FSEEKI64 1
 #endif
+#ifdef _USE_MATH_DEFINES
+#define HAVE_M_PI 1
 #endif
-#if !defined(_MSC_VER) || defined(_USE_MATH_DEFINES)
+#elif defined(__WATCOMC__)
+#define HAVE__FSEEKI64 1
+#define HAVE_STRTOLL 1
+#define HAVE_STRTOULL 1
+#define HAVE_VSSCANF 1
+#define HAVE_ROUND 1
+#define HAVE_SCALBN 1
+#define HAVE_TRUNC  1
+#else
 #define HAVE_M_PI 1
 #endif
 #else
@@ -228,7 +246,9 @@ typedef unsigned int uintptr_t;
 #endif
 
 /* Enable various audio drivers */
+#if defined(HAVE_MMDEVICEAPI_H) && defined(HAVE_AUDIOCLIENT_H)
 #define SDL_AUDIO_DRIVER_WASAPI 1
+#endif
 #define SDL_AUDIO_DRIVER_DSOUND 1
 #define SDL_AUDIO_DRIVER_WINMM  1
 #define SDL_AUDIO_DRIVER_DISK   1
@@ -249,7 +269,11 @@ typedef unsigned int uintptr_t;
 #define SDL_HAPTIC_XINPUT   1
 
 /* Enable the sensor driver */
+#ifdef HAVE_SENSORSAPI_H
 #define SDL_SENSOR_WINDOWS  1
+#else
+#define SDL_SENSOR_DUMMY    1
+#endif
 
 /* Enable various shared object loading systems */
 #define SDL_LOADSO_WINDOWS  1
diff --git a/src/core/windows/SDL_windows.h b/src/core/windows/SDL_windows.h
index 917a8256f..681f01b87 100644
--- a/src/core/windows/SDL_windows.h
+++ b/src/core/windows/SDL_windows.h
@@ -30,6 +30,8 @@
 #ifndef UNICODE
 #define UNICODE 1
 #endif
+#undef WINVER
+#define WINVER 0x0501
 #undef _WIN32_WINNT
 #define _WIN32_WINNT  0x501   /* Need 0x410 for AlphaBlend() and 0x500 for EnumDisplayDevices(), 0x501 for raw input */
 #endif
diff --git a/src/dynapi/SDL_dynapi.h b/src/dynapi/SDL_dynapi.h
index dddc094c1..330b3426c 100644
--- a/src/dynapi/SDL_dynapi.h
+++ b/src/dynapi/SDL_dynapi.h
@@ -61,7 +61,7 @@
 #define SDL_DYNAMIC_API 0  /* vitasdk doesn't support dynamic linking */
 #elif defined(__NGAGE__)
 #define SDL_DYNAMIC_API 0  /* The N-Gage doesn't support dynamic linking either */
-#elif defined(__OS2__)
+#elif defined(__OS2__) || defined(__WATCOMC__)
 #define SDL_DYNAMIC_API 0  /* see github bugs #5667 and #5669 */
 #elif defined(DYNAPI_NEEDS_DLOPEN) && !defined(HAVE_DLOPEN)
 #define SDL_DYNAMIC_API 0  /* we need dlopen(), but don't have it.... */
diff --git a/src/render/direct3d/SDL_render_d3d.c b/src/render/direct3d/SDL_render_d3d.c
index 51f6c77be..97047f4bf 100644
--- a/src/render/direct3d/SDL_render_d3d.c
+++ b/src/render/direct3d/SDL_render_d3d.c
@@ -41,6 +41,13 @@
 
 #include "SDL_shaders_d3d.h"
 
+#ifdef __WATCOMC__
+/* FIXME: Remove this once https://github.com/open-watcom/open-watcom-v2/pull/868 is merged */
+#define D3DBLENDOP_REVSUBTRACT 3
+/* FIXME: Remove this once https://github.com/open-watcom/open-watcom-v2/pull/869 is merged */
+#define D3DERR_UNSUPPORTEDCOLOROPERATION MAKE_D3DHRESULT( 2073 )
+#endif
+
 typedef struct
 {
     SDL_Rect viewport;
diff --git a/src/video/windows/SDL_windowsvideo.c b/src/video/windows/SDL_windowsvideo.c
index 4bd2a9831..93a6bfa81 100644
--- a/src/video/windows/SDL_windowsvideo.c
+++ b/src/video/windows/SDL_windowsvideo.c
@@ -35,6 +35,22 @@
 #include "SDL_windowsshape.h"
 #include "SDL_windowsvulkan.h"
 
+#ifdef D3D_DEBUG_INFO
+#ifndef D3D_SDK_VERSION
+#define D3D_SDK_VERSION   (32 | 0x80000000)
+#endif
+#ifndef D3D9b_SDK_VERSION
+#define D3D9b_SDK_VERSION (31 | 0x80000000)
+#endif
+#else /**/
+#ifndef D3D_SDK_VERSION
+#define D3D_SDK_VERSION   32
+#endif
+#ifndef D3D9b_SDK_VERSION
+#define D3D9b_SDK_VERSION 31
+#endif
+#endif
+
 /* Initialization/Query functions */
 static int WIN_VideoInit(_THIS);
 static void WIN_VideoQuit(_THIS);
diff --git a/test/Makefile.w32 b/test/Makefile.w32
new file mode 100644
index 000000000..5e3e6bcaa
--- /dev/null
+++ b/test/Makefile.w32
@@ -0,0 +1,17 @@
+# Open Watcom makefile to build SDL2 tests for Win32
+# wmake -f Makefile.w32
+
+SYSTEM = nt
+
+INCPATH = -I"$(%WATCOM)/h/nt" -I"$(%WATCOM)/h" -I"../src/video/khronos"
+
+CFLAGS = -bt=nt -d0 -q -bm -5s -fp5 -fpi87 -sg -oteanbmier -ei
+CFLAGS+= -wx -wcd=303
+CFLAGS+= -DSDL_MAIN_HANDLED
+
+CFLAGS+= -DHAVE_OPENGL
+GLLIBS = opengl32.lib
+
+TNSRCS = testnative.obj testnativew32.obj
+
+!include watcom.mif
diff --git a/test/versioning.sh b/test/versioning.sh
index 1e160bc26..3a05c6243 100755
--- a/test/versioning.sh
+++ b/test/versioning.sh
@@ -56,6 +56,17 @@ else
     not_ok "Makefile.os2 $version disagrees with SDL_version.h $ref_version"
 fi
 
+major=$(sed -ne 's/^MAJOR_VERSION *= *//p' Makefile.w32)
+minor=$(sed -ne 's/^MINOR_VERSION *= *//p' Makefile.w32)
+micro=$(sed -ne 's/^MICRO_VERSION *= *//p' Makefile.w32)
+version="${major}.${minor}.${micro}"
+
+if [ "$ref_version" = "$version" ]; then
+    ok "Makefile.w32 $version"
+else
+    not_ok "Makefile.w32 $version disagrees with SDL_version.h $ref_version"
+fi
+
 version=$(sed -Ene 's/^[$]SDLVersion = "([0-9.]+)"\r?$/\1/p' build-scripts/winrtbuild.ps1)
 
 if [ "$ref_version" = "$version" ]; then
diff --git a/test/watcom.mif b/test/watcom.mif
index 5bf10bef3..4cc8e7e3a 100644
--- a/test/watcom.mif
+++ b/test/watcom.mif
@@ -64,6 +64,9 @@ testoverlay2.exe: testoverlay2.obj testyuv_cvt.obj
 testyuv.exe: testyuv.obj testyuv_cvt.obj
   wlink SYS $(SYSTEM) libpath $(LIBPATH) lib {$(LIBS)} op q op el file {$<} name $@
 
+testshader.exe: testshader.obj
+  wlink SYS $(SYSTEM) libpath $(LIBPATH) lib {$(LIBS) $(GLLIBS)} op q op el file {$<} name $@
+
 testime.exe: testime.obj
   wlink SYS $(SYSTEM) libpath $(LIBPATH) lib {$(LIBS) $(TTFLIBS)} op q op el file {$<} name $@