diff --git a/Makefile.in b/Makefile.in
index 0d2fc31..645da6d 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -64,7 +64,7 @@ AR=@AR@
 RANLIB=@RANLIB@
 STRIP=@STRIP@
 INSTALL=@INSTALL@
-CFLAGS=@CFLAGS@
+CFLAGS=-Ilibtomcrypt @CFLAGS@
 LIBS=$(LTC) $(LTM) @LIBS@
 LDFLAGS=@LDFLAGS@