Index: H5Gname.c
===================================================================
--- H5Gname.c	(revision 154119)
+++ H5Gname.c	(revision 154120)
@@ -829,6 +829,14 @@
                 HGOTO_DONE(SUCCEED)     /* Do not exit search over IDs */
 
             oloc = H5T_oloc((H5T_t *)obj_ptr);
+
+            /* Some datatypes can come through here with NULL files, such as
+             * those explicitly set in H5T_conv_struct_init(). They aren't
+             * visible to clients so don't bother trying to rename them.
+             */
+            if (oloc->file == NULL)
+                HGOTO_DONE(SUCCEED)     /* Do not exit search over IDs */
+
             obj_path = H5T_nameof((H5T_t *)obj_ptr);
             break;