diff --git a/src/arbits/slbt_archive_meta.c b/src/arbits/slbt_archive_meta.c
index f3dd39e..7279602 100644
--- a/src/arbits/slbt_archive_meta.c
+++ b/src/arbits/slbt_archive_meta.c
@@ -842,6 +842,18 @@ int slbt_get_archive_meta(
 			if (m->memberv[idx]->ar_member_data == arlongnames)
 				m->armeta.a_arref_longnames = m->memberv[idx];
 
+	/* common binary format (information only) */
+	for (idx=0,nmembers=0; idx<nentries; idx++) {
+		if (m->memberv[idx]->ar_member_attr == AR_MEMBER_ATTR_OBJECT) {
+			if (m->ofmtattr && (m->ofmtattr != m->memberv[idx]->ar_object_attr)) {
+				m->ofmtattr = 0;
+				idx = nentries;
+			} else if (!m->ofmtattr) {
+				m->ofmtattr = m->memberv[idx]->ar_object_attr;
+			}
+		}
+	}
+
 	/* member vector */
 	m->armeta.a_memberv = m->memberv;
 
diff --git a/src/internal/slibtool_ar_impl.h b/src/internal/slibtool_ar_impl.h
index b034c2b..e5bfca8 100644
--- a/src/internal/slibtool_ar_impl.h
+++ b/src/internal/slibtool_ar_impl.h
@@ -36,6 +36,7 @@ struct ar_armaps_impl {
 
 struct slbt_archive_meta_impl {
 	const struct slbt_driver_ctx *  dctx;
+	size_t                          ofmtattr;
 	size_t                          nentries;
 	void *                          hdrinfov;
 	char *                          namestrs;