diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 14feabd..b30cb4f 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -2164,6 +2164,9 @@
     if( !PSA_ALG_IS_HASH( alg ) )
         return( PSA_ERROR_INVALID_ARGUMENT );
 
+    /* Ensure all of the context is zeroized, not just the dummy int */
+    memset( &operation->ctx, 0, sizeof( operation->ctx ) );
+
     return( psa_driver_wrapper_hash_setup( operation, alg ) );
 }