diff --git a/aegisub/Makefile.am b/aegisub/Makefile.am
index 09d5ee41dfb224544254a6e23ae3fa4583701c65..671ab08ce27198762c29abe48c30dd7a05516a51 100644
--- a/aegisub/Makefile.am
+++ b/aegisub/Makefile.am
@@ -4,7 +4,7 @@ noinst_LIBRARIES=
 
 SUBDIRS = bitmaps posix
 
-AM_CXXFLAGS = -DAEGISUB -Iposix -include posix/defines.h @WX_CPPFLAGS@
+AM_CXXFLAGS = -DAEGISUB -Iposix -include posix/defines.h -Iinclude @WX_CPPFLAGS@
 
 bin_PROGRAMS = aegisub
 aegisub_LDADD = posix/libposix.a