diff --git a/programs/pkey/pk_sign.c b/programs/pkey/pk_sign.c
index 88561b1..e85350d 100644
--- a/programs/pkey/pk_sign.c
+++ b/programs/pkey/pk_sign.c
@@ -32,6 +32,7 @@
 #include <stdio.h>
 #define polarssl_snprintf   snprintf
 #define polarssl_printf     printf
+#define polarssl_snprintf   snprintf
 #endif
 
 #if defined(POLARSSL_BIGNUM_C) && defined(POLARSSL_ENTROPY_C) && \