diff --git a/Makefile b/Makefile
index ca9f16d19a969e..aac4b670448af3 100644
--- a/Makefile
+++ b/Makefile
@@ -629,6 +629,7 @@ TEST_PROGRAMS_NEED_X += test-scrap-cache-tree
 TEST_PROGRAMS_NEED_X += test-sha1
 TEST_PROGRAMS_NEED_X += test-sha1-array
 TEST_PROGRAMS_NEED_X += test-sigchain
+TEST_PROGRAMS_NEED_X += test-strcmp-offset
 TEST_PROGRAMS_NEED_X += test-string-list
 TEST_PROGRAMS_NEED_X += test-submodule-config
 TEST_PROGRAMS_NEED_X += test-subprocess
diff --git a/t/helper/.gitignore b/t/helper/.gitignore
index d6e8b3679872ab..0a89531a8b7f85 100644
--- a/t/helper/.gitignore
+++ b/t/helper/.gitignore
@@ -25,6 +25,7 @@
 /test-sha1
 /test-sha1-array
 /test-sigchain
+/test-strcmp-offset
 /test-string-list
 /test-submodule-config
 /test-subprocess
diff --git a/t/helper/test-strcmp-offset.c b/t/helper/test-strcmp-offset.c
new file mode 100644
index 00000000000000..56fd8c1e41b5eb
--- /dev/null
+++ b/t/helper/test-strcmp-offset.c
@@ -0,0 +1,59 @@
+#include "cache.h"
+
+struct test_data {
+	const char *s1;
+	const char *s2;
+	int first_change;
+};
+
+static struct test_data data[] = {
+	{ "abc", "abc", 0 },
+	{ "abc", "def", 0 },
+
+	{ "abc", "abz", 2 },
+
+	{ "abc", "abcdef", 3 },
+
+	{ "abc\xF0zzz", "abc\xFFzzz", 3 },
+
+	{ NULL, NULL, 0 }
+};
+
+int try_pair(const char *sa, const char *sb, int first_change)
+{
+	int failed = 0;
+	int offset, r_exp, r_tst;
+
+	r_exp = strcmp(sa, sb);
+	r_tst = strcmp_offset(sa, sb, &offset);
+	if (r_tst != r_exp) {
+		if ((r_tst < 0 && r_exp < 0) || (r_tst > 0 && r_exp > 0))
+			warning("'%s' vs '%s', imprecise result: %d != %d",
+				sa, sb, r_exp, r_tst);
+		else {
+			error("'%s' vs '%s', result expect %d, observed %d",
+			      sa, sb, r_exp, r_tst);
+			failed = 1;
+		}
+	}
+	if (offset != first_change) {
+		error("'%s' vs '%s', offset expect %d, observed %d",
+		      sa, sb, first_change, offset);
+		failed = 1;
+	}
+
+	return failed;
+}
+
+int cmd_main(int argc, const char **argv)
+{
+	int failed = 0;
+	int k;
+
+	for (k=0; data[k].s1; k++) {
+		failed += try_pair(data[k].s1, data[k].s2, data[k].first_change);
+		failed += try_pair(data[k].s2, data[k].s1, data[k].first_change);
+	}
+
+	return failed;
+}
diff --git a/t/t0065-strcmp-offset.sh b/t/t0065-strcmp-offset.sh
new file mode 100755
index 00000000000000..0176c8c9243e09
--- /dev/null
+++ b/t/t0065-strcmp-offset.sh
@@ -0,0 +1,11 @@
+#!/bin/sh
+
+test_description='Test strcmp_offset functionality'
+
+. ./test-lib.sh
+
+test_expect_success run_helper '
+	test-strcmp-offset
+'
+
+test_done