diff --git a/library/rsa.c b/library/rsa.c
index 6dfcdb3..b9d6bec 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -34,7 +34,10 @@
 #if defined(POLARSSL_RSA_C)
 
 #include "polarssl/rsa.h"
+
+#if defined(POLARSSL_PKCS1_V21)
 #include "polarssl/md.h"
+#endif
 
 #include <stdlib.h>
 #include <stdio.h>