diff --git a/Makefile b/Makefile
index bddd41f..9154d07 100644
--- a/Makefile
+++ b/Makefile
@@ -45,7 +45,7 @@ ${LIBUCONTEXT_SONAME}: ${LIBUCONTEXT_NAME}
 	$(CC) -std=c99 -D_BSD_SOURCE -fPIC -DPIC ${CFLAGS} ${CPPFLAGS} -c -o $@ $<
 
 .S.o:
-	$(CC) -fPIC -DPIC ${CFLAGS} ${CPPFLAGS} -c -o $@ $<
+	$(CC) -fPIC -DPIC -DLIBUCONTEXT_ASSEMBLY ${CFLAGS} ${CPPFLAGS} -c -o $@ $<
 
 clean:
 	rm -f ${LIBUCONTEXT_NAME} ${LIBUCONTEXT_SONAME} ${LIBUCONTEXT_STATIC_NAME} \