diff --git a/Makefile.mingw b/Makefile.mingw
index 81be2ff65e..306a41cc05 100644
--- a/Makefile.mingw
+++ b/Makefile.mingw
@@ -25,7 +25,7 @@ RELEASEOBJDIR ?= releaseobj
 CCDV ?= @ccdv
 RE2C = tools/re2c/re2c
 
-CPPFLAGS = -DWIN32 -D_WIN32 -D_WINDOWS -DHAVE_STRUPR -DHAVE_FILELENGTH -DI_DO_NOT_LIKE_BIG_DOWNLOADS -D__forceinline=inline -MMD -Izlib -IFLAC -Ijpeg-6b -Isrc -Isrc/win32 -Isrc/g_doom -Isrc/g_heretic -I src/g_hexen -Isrc/g_raven -Isrc/g_strife -Isrc/g_shared -Isrc/oplsynth -Isrc/sound
+CPPFLAGS = -DWIN32 -D_WIN32 -D_WINDOWS -DHAVE_STRUPR -DHAVE_FILELENGTH -DI_DO_NOT_LIKE_BIG_DOWNLOADS -D__forceinline=inline -MMD -Izlib -IFLAC -Ijpeg-6b -Isrc -Isrc/win32 -Isrc/g_doom -Isrc/g_heretic -Isrc/g_hexen -Isrc/g_raven -Isrc/g_strife -Isrc/g_shared -Isrc/oplsynth -Isrc/sound -Isrc/textures -Isrc/thingdef
 LDFLAGS += flac/libflac.a zlib/libz.a jpeg-6b/libjpeg.a -lfmod -lwsock32 -lwinmm -lddraw -ldsound -ldxguid -ldinput8 -lole32 -luser32 -lgdi32 -lcomctl32 -lcomdlg32 -lsetupapi -lws2_32 -Wl,--subsystem,windows
 
 ifdef FMODDIR
@@ -52,7 +52,7 @@ ifeq ($(CONFIG),Release)
   TARGET = $(RELEASETARGET)
 endif
 
-SRCDIRS = src/ $(addprefix src/,g_doom/ g_heretic/ g_hexen/ g_raven/ g_shared/ g_strife/ oplsynth/ sound/ win32/ textures/)
+SRCDIRS = src/ $(addprefix src/,g_doom/ g_heretic/ g_hexen/ g_raven/ g_shared/ g_strife/ oplsynth/ sound/ win32/ textures/ thingdef/)
 VPATH = $(SRCDIRS)
 
 CPPSRCS = $(wildcard $(addsuffix *.cpp,$(SRCDIRS)))