diff --git a/library/asn1write.c b/library/asn1write.c
index dc61854..2110052 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -472,7 +472,7 @@
         cur->val.len = val_len;
     }
 
-    if( val != NULL )
+    if( val != NULL && val_len != 0 )
         memcpy( cur->val.p, val, val_len );
 
     return( cur );