diff --git a/library/psa_util.c b/library/psa_util.c
index dfea36b..be257e7 100644
--- a/library/psa_util.c
+++ b/library/psa_util.c
@@ -489,7 +489,7 @@
     }
 
     /* Skip possible leading zero */
-    if ((*p == 0x00) && (unpadded_len > 0)) {
+    if ((unpadded_len > 0) && (*p == 0x00)) {
         p++;
         unpadded_len--;
         /* It should never happen that the input number is all zeros. */