diff --git a/compat/Makefile.am b/compat/Makefile.am
index d4aa3b8..40ea83d 100644
--- a/compat/Makefile.am
+++ b/compat/Makefile.am
@@ -13,7 +13,7 @@
 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 # OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
-AM_CPPFLAGS = -I$(top_srcdir)/include -I$(top_srcdir)/src
+AM_CPPFLAGS = -I$(top_srcdir)/include -I$(top_srcdir)/src -DSHA2_SMALL
 
 noinst_LTLIBRARIES = libcompat.la libcompatnoopt.la
 
diff --git a/include/Makefile.am b/include/Makefile.am
index b40ac03..b1be9f9 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -2,7 +2,6 @@ noinst_HEADERS =
 noinst_HEADERS += signal.h
 noinst_HEADERS += unistd.h
 noinst_HEADERS += machine/endian.h
-noinst_HEADERS += sys/cdefs.h
 noinst_HEADERS += sys/queue.h
 noinst_HEADERS += sys/socket.h
 noinst_HEADERS += sys/types.h
diff --git a/include/sys/cdefs.h b/include/sys/cdefs.h
deleted file mode 100644
index 77ff9a5..0000000
--- a/include/sys/cdefs.h
+++ /dev/null
@@ -1,14 +0,0 @@
-/*
- * Public domain
- * sys/cdefs.h compatibility shim
- */
-
-#include_next <sys/cdefs.h>
-
-#ifndef __weak_alias
-/*
- * We do not use any of the SHA function aliases that this would provide in
- * OpenNTPD
- */
-#define __weak_alias(alias,sym)
-#endif