diff --git a/aegisub/Makefile.am b/aegisub/Makefile.am
index de71908bd..cbc80bbe2 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 -Iinclude @WX_CPPFLAGS@
+AM_CXXFLAGS = -DAEGISUB -Iposix -include posix/defines.h -Iinclude @WX_CPPFLAGS@ @OPENMP_CXXFLAGS@
 
 bin_PROGRAMS = aegisub
 aegisub_LDADD = posix/libposix.a