diff --git a/library/pk.c b/library/pk.c
index d8801b5..52bcb86 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -363,9 +363,9 @@
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     if( ctx->pk_info->signature_size_func == NULL )
-        return( ( ctx->pk_info->get_bitlen( ctx->pk_ctx ) + 7 ) / 8 );
-    else
-        return( ctx->pk_info->signature_size_func( ctx->pk_ctx ) );
+        return( 0 );
+
+    return( ctx->pk_info->signature_size_func( ctx->pk_ctx ) );
 }
 
 /*