diff --git a/reftable/basics.c b/reftable/basics.c
index e969927b61..f0442a46cf 100644
--- a/reftable/basics.c
+++ b/reftable/basics.c
@@ -152,6 +152,9 @@ size_t binsearch(size_t sz, int (*f)(size_t k, void *args), void *args)
 	size_t lo = 0;
 	size_t hi = sz;
 
+	if (!sz)
+		return 0;
+
 	/* Invariants:
 	 *
 	 *  (hi == sz) || f(hi) == true
diff --git a/t/unit-tests/u-reftable-basics.c b/t/unit-tests/u-reftable-basics.c
index 73566ed0eb..c5d83b6714 100644
--- a/t/unit-tests/u-reftable-basics.c
+++ b/t/unit-tests/u-reftable-basics.c
@@ -60,6 +60,17 @@ void test_reftable_basics__binsearch(void)
 	}
 }
 
+static int unreachable_lesseq(size_t i UNUSED, void *args UNUSED)
+{
+	cl_fail("comparison function called for empty range");
+	return 0;
+}
+
+void test_reftable_basics__binsearch_empty(void)
+{
+	cl_assert_equal_i(binsearch(0, &unreachable_lesseq, NULL), 0);
+}
+
 void test_reftable_basics__names_length(void)
 {
 	const char *a[] = { "a", "b", NULL };