diff --git a/tests/Makefile.am b/tests/Makefile.am
index ea4bc98..58fd513 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -9,6 +9,7 @@ check_check_SOURCES = \
 	check_file_t.c \
         check_exception_t.c \
         check_calibrate.c
+check_check_CPPFLAGS= $(CPPFLAGS)
 check_check_CFLAGS= $(CFLAGS) $(CHECK_CFLAGS)
 check_check_LDFLAGS= $(LDFLAGS) $(CHECK_LIBS)
 check_check_LDADD = $(top_builddir)/src/libmodetw.la