diff --git a/builtin/rebase.c b/builtin/rebase.c
index 5b3e5baec8..1c6f817f4b 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -1481,10 +1481,15 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	if (options.flags & REBASE_DIFFSTAT) {
 		struct diff_options opts;
 
-		if (options.flags & REBASE_VERBOSE)
-			printf(_("Changes from %s to %s:\n"),
-				oid_to_hex(&merge_base),
-				oid_to_hex(&options.onto->object.oid));
+		if (options.flags & REBASE_VERBOSE) {
+			if (is_null_oid(&merge_base))
+				printf(_("Changes to %s:\n"),
+				       oid_to_hex(&options.onto->object.oid));
+			else
+				printf(_("Changes from %s to %s:\n"),
+				       oid_to_hex(&merge_base),
+				       oid_to_hex(&options.onto->object.oid));
+		}
 
 		/* We want color (if set), but no pager */
 		diff_setup(&opts);
@@ -1494,8 +1499,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 		opts.detect_rename = DIFF_DETECT_RENAME;
 		diff_setup_done(&opts);
-		diff_tree_oid(&merge_base, &options.onto->object.oid,
-			      "", &opts);
+		diff_tree_oid(is_null_oid(&merge_base) ?
+			      the_hash_algo->empty_tree : &merge_base,
+			      &options.onto->object.oid, "", &opts);
 		diffcore_std(&opts);
 		diff_flush(&opts);
 	}
diff --git a/git-legacy-rebase.sh b/git-legacy-rebase.sh
index b97ffdc9dd..b4c7dbfa57 100755
--- a/git-legacy-rebase.sh
+++ b/git-legacy-rebase.sh
@@ -718,10 +718,16 @@ if test -n "$diffstat"
 then
 	if test -n "$verbose"
 	then
-		echo "$(eval_gettext "Changes from \$mb to \$onto:")"
+		if test -z "$mb"
+		then
+			echo "$(eval_gettext "Changes to \$onto:")"
+		else
+			echo "$(eval_gettext "Changes from \$mb to \$onto:")"
+		fi
 	fi
+	mb_tree="${mb:-$(git hash-object -t tree /dev/null)}"
 	# We want color (if set), but no pager
-	GIT_PAGER='' git diff --stat --summary "$mb" "$onto"
+	GIT_PAGER='' git diff --stat --summary "$mb_tree" "$onto"
 fi
 
 test -n "$interactive_rebase" && run_specific_rebase
diff --git a/t/t3406-rebase-message.sh b/t/t3406-rebase-message.sh
index 38bd876cab..c2c9950568 100755
--- a/t/t3406-rebase-message.sh
+++ b/t/t3406-rebase-message.sh
@@ -91,4 +91,14 @@ test_expect_success 'error out early upon -C<n> or --whitespace=<bad>' '
 	test_i18ngrep "Invalid whitespace option" err
 '
 
+test_expect_success 'rebase -i onto unrelated history' '
+	git init unrelated &&
+	test_commit -C unrelated 1 &&
+	git -C unrelated remote add -f origin "$PWD" &&
+	git -C unrelated branch --set-upstream-to=origin/master &&
+	git -C unrelated -c core.editor=true rebase -i -v --stat >actual &&
+	test_i18ngrep "Changes to " actual &&
+	test_i18ngrep "5 files changed" actual
+'
+
 test_done