diff --git a/library/pk.c b/library/pk.c
index f25266a..1eab65a 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -256,7 +256,8 @@
         return( 0 );
 
     /* Filter out non allowed usage flags */
-    if( ( usage & ~( PSA_KEY_USAGE_SIGN_HASH |
+    if( usage == 0 ||
+        ( usage & ~( PSA_KEY_USAGE_SIGN_HASH |
                      PSA_KEY_USAGE_DECRYPT |
                      PSA_KEY_USAGE_DERIVE ) ) != 0 )
         return( 0 );