diff --git a/library/x509_crt.c b/library/x509_crt.c
index 3e505e2f3..76558342e 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -2179,7 +2179,7 @@ static int x509_crt_find_parent(
     }
 
     /* extra precaution against mistakes in the caller */
-    if( parent == NULL )
+    if( *parent == NULL )
     {
         *parent_is_trusted = 0;
         *signature_is_good = 0;