diff --git a/include/polarssl/md4.h b/include/polarssl/md4.h
index 641edf1..4791fb1 100644
--- a/include/polarssl/md4.h
+++ b/include/polarssl/md4.h
@@ -152,6 +152,9 @@
  */
 int md4_self_test( int verbose );
 
+/* Internal use */
+void md4_process( md4_context *ctx, const unsigned char data[64] );
+
 #ifdef __cplusplus
 }
 #endif