diff --git a/git-submodule.sh b/git-submodule.sh
index 1b568e29b9..c09eb3e03d 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -82,6 +82,11 @@ isnumber()
 	n=$(($1 + 0)) 2>/dev/null && test "$n" = "$1"
 }
 
+# Given a full hex object ID, is this the zero OID?
+is_zero_oid () {
+	echo "$1" | sane_egrep '^0+$' >/dev/null 2>&1
+}
+
 # Sanitize the local git environment for use within a submodule. We
 # can't simply use clear_local_git_env since we want to preserve some
 # of the settings from GIT_CONFIG_PARAMETERS.
@@ -780,7 +785,7 @@ cmd_summary() {
 	while read -r mod_src mod_dst sha1_src sha1_dst status name
 	do
 		if test -z "$cached" &&
-			test $sha1_dst = 0000000000000000000000000000000000000000
+			is_zero_oid $sha1_dst
 		then
 			case "$mod_dst" in
 			160000)