Index: configure.ac
--- configure.ac.orig
+++ configure.ac
@@ -14,7 +14,7 @@ PKG_CHECK_MODULES([FFTW3], [fftw3])
 
 # Needed for unit tests and the demo app.
 with_demo_app=yes
-PKG_CHECK_MODULES([SDL2], [sdl2])
+PKG_CHECK_MODULES([SDL2], [sdl2], [], [x=x])
 
 # This is only needed for the demo app.
 PKG_CHECK_MODULES([SDL2_image], [SDL2_image], [], [with_demo_app=no; AC_MSG_WARN([SDL2_image not found, demo program will not be built])])
