diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6f5c43ac0..4e4223e9f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Increase minimum gpgme version [#405](https://github.com/greenbone/gvm-libs/pull/405)
 - Always NULL check ifaddrs->ifa_addr [#416](https://github.com/greenbone/gvm-libs/pull/416)
 - Correct g_hash_table_remove arg [#419](https://github.com/greenbone/gvm-libs/pull/419)
+- Accept underscore as valid char in hostname strings [#429](https://github.com/greenbone/gvm-libs/pull/429)
 
 [20.8.1]: https://github.com/greenbone/gvm-libs/compare/v20.8.0...gvm-libs-20.08
 
diff --git a/base/hosts.c b/base/hosts.c
index d1e8ed6c1..502e4a2d0 100644
--- a/base/hosts.c
+++ b/base/hosts.c
@@ -454,7 +454,7 @@ is_hostname (const char *str)
 
   point = split;
   while (*point)
-    if (g_regex_match_simple ("^(?!-)[a-z0-9-]{1,63}(?<!-)$", *point,
+    if (g_regex_match_simple ("^(?!-)[a-z0-9_-]{1,63}(?<!-)$", *point,
                               G_REGEX_CASELESS, 0)
         == 0)
       {
diff --git a/base/hosts_tests.c b/base/hosts_tests.c
index cc45d2677..a8e3d9275 100644
--- a/base/hosts_tests.c
+++ b/base/hosts_tests.c
@@ -65,6 +65,10 @@ Ensure (hosts, gvm_get_host_type_returns_host_type_hostname)
 {
   assert_that (gvm_get_host_type ("www.greenbone.net"),
                is_equal_to (HOST_TYPE_NAME));
+  assert_that (gvm_get_host_type ("www.example_underscore.net"),
+               is_equal_to (HOST_TYPE_NAME));
+  assert_that (gvm_get_host_type ("www.example-dash.net"),
+               is_equal_to (HOST_TYPE_NAME));
   assert_that (gvm_get_host_type ("greenbone.net"),
                is_equal_to (HOST_TYPE_NAME));
   assert_that (gvm_get_host_type ("g"), is_equal_to (HOST_TYPE_NAME));