diff --git a/lib/isc/hashmap.c b/lib/isc/hashmap.c
index 0abb1220c2..2ea7a25182 100644
--- a/lib/isc/hashmap.c
+++ b/lib/isc/hashmap.c
@@ -134,7 +134,7 @@ try_nexttable(const isc_hashmap_t *hashmap, uint8_t idx) {
 static void
 hashmap_node_init(hashmap_node_t *node, const uint32_t hashval,
 		  const uint8_t *key, const uint32_t keysize, void *value) {
-	REQUIRE(key != NULL && keysize > 0 && keysize <= UINT16_MAX);
+	REQUIRE(key != NULL && keysize <= UINT16_MAX);
 
 	*node = (hashmap_node_t){
 		.value = value,
@@ -318,7 +318,6 @@ uint32_t
 isc_hashmap_hash(const isc_hashmap_t *hashmap, const void *key,
 		 uint32_t keysize) {
 	REQUIRE(ISC_HASHMAP_VALID(hashmap));
-	REQUIRE(key != NULL && keysize > 0 && keysize <= UINT16_MAX);
 
 	uint32_t hashval;
 
@@ -332,7 +331,7 @@ isc_result_t
 isc_hashmap_find(const isc_hashmap_t *hashmap, const uint32_t *hashvalp,
 		 const void *key, uint32_t keysize, void **valuep) {
 	REQUIRE(ISC_HASHMAP_VALID(hashmap));
-	REQUIRE(key != NULL && keysize > 0 && keysize <= UINT16_MAX);
+	REQUIRE(key != NULL && keysize <= UINT16_MAX);
 
 	hashmap_node_t *node;
 	uint8_t idx = hashmap->hindex;
@@ -487,7 +486,7 @@ isc_result_t
 isc_hashmap_delete(isc_hashmap_t *hashmap, const uint32_t *hashvalp,
 		   const void *key, uint32_t keysize) {
 	REQUIRE(ISC_HASHMAP_VALID(hashmap));
-	REQUIRE(key != NULL && keysize > 0 && keysize <= UINT16_MAX);
+	REQUIRE(key != NULL && keysize <= UINT16_MAX);
 
 	hashmap_node_t *node;
 	isc_result_t result = ISC_R_NOTFOUND;
@@ -600,7 +599,7 @@ isc_result_t
 isc_hashmap_add(isc_hashmap_t *hashmap, const uint32_t *hashvalp,
 		const void *key, uint32_t keysize, void *value) {
 	REQUIRE(ISC_HASHMAP_VALID(hashmap));
-	REQUIRE(key != NULL && keysize > 0 && keysize <= UINT16_MAX);
+	REQUIRE(key != NULL && keysize <= UINT16_MAX);
 
 	isc_result_t result;
 	uint32_t hashval = (hashvalp != NULL)
diff --git a/tests/isc/hashmap_test.c b/tests/isc/hashmap_test.c
index 334ed8d64f..99b7951f57 100644
--- a/tests/isc/hashmap_test.c
+++ b/tests/isc/hashmap_test.c
@@ -351,6 +351,30 @@ ISC_RUN_TEST_IMPL(isc_hashmap_iterator) {
 	return;
 }
 
+ISC_RUN_TEST_IMPL(isc_hashmap_hash_zero_length) {
+	isc_hashmap_t *hashmap = NULL;
+	uint32_t hashval;
+	bool again = false;
+
+again:
+	isc_hashmap_create(mctx, 1, ISC_HASHMAP_CASE_SENSITIVE, &hashmap);
+
+	hashval = isc_hashmap_hash(hashmap, "", 0);
+
+	isc_hashmap_destroy(&hashmap);
+
+	if (hashval == 0 && !again) {
+		/*
+		 * We could be extremely unlock and the siphash could hash the
+		 * zero length string to 0, so try one more time.
+		 */
+		again = true;
+		goto again;
+	}
+
+	assert_int_not_equal(hashval, 0);
+}
+
 ISC_RUN_TEST_IMPL(isc_hashmap_case) {
 	isc_result_t result;
 	isc_hashmap_t *hashmap = NULL;
@@ -401,6 +425,7 @@ ISC_RUN_TEST_IMPL(isc_hashmap_case) {
 }
 
 ISC_TEST_LIST_START
+ISC_TEST_ENTRY(isc_hashmap_hash_zero_length)
 ISC_TEST_ENTRY(isc_hashmap_case)
 ISC_TEST_ENTRY(isc_hashmap_1_120)
 ISC_TEST_ENTRY(isc_hashmap_6_1000)