diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 9c645ef..c5f9601 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -2226,6 +2226,11 @@
     if( operation->id == 0 )
         return( PSA_ERROR_BAD_STATE );
 
+    /* Don't require hash implementations to behave correctly on a
+     * zero-length input, which may have an invalid pointer. */
+    if( input_length == 0 )
+        return( PSA_SUCCESS );
+
     psa_status_t status = psa_driver_wrapper_hash_update( operation,
                                                           input, input_length );
     if( status != PSA_SUCCESS )