diff --git a/programs/psa/key_ladder_demo.c b/programs/psa/key_ladder_demo.c
index 2734ceb..0ea434f 100644
--- a/programs/psa/key_ladder_demo.c
+++ b/programs/psa/key_ladder_demo.c
@@ -392,6 +392,7 @@
     input_file = NULL;
 
     /* Construct a header. */
+    memset(&header, 0, sizeof(header));
     memcpy(&header.magic, WRAPPED_DATA_MAGIC, WRAPPED_DATA_MAGIC_LENGTH);
     header.ad_size = sizeof(header);
     header.payload_size = input_size;