diff --git a/man/sd_bus_is_open.xml b/man/sd_bus_is_open.xml
index 8e0aed29b3..621ed272bb 100644
--- a/man/sd_bus_is_open.xml
+++ b/man/sd_bus_is_open.xml
@@ -57,6 +57,9 @@
     zero outside of this state, and positive otherwise. Effectively, this function returns positive while regular
     messages can be sent or received on the connection.</para>
 
+    <para>The <parameter>bus</parameter> argument may be <constant>NULL</constant>, zero is also returned in
+    that case.</para>
+
     <para>To be notified when the connection is fully established, use
     <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
     install a match for the <function>Connected()</function> signal on the
@@ -68,8 +71,8 @@
   <refsect1>
     <title>Return Value</title>
 
-    <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
-    error code.</para>
+    <para>Those functions return 0 if the bus is <emphasis>not</emphasis> in the given state, and a positive
+    integer when it is. On failure, a negative errno-style error code is returned.</para>
 
     <refsect2>
       <title>Errors</title>
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index e719c74370..2f4e67c97e 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -1800,7 +1800,9 @@ void bus_enter_closing(sd_bus *bus) {
 DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_bus, sd_bus, bus_free);
 
 _public_ int sd_bus_is_open(sd_bus *bus) {
-        assert_return(bus, -EINVAL);
+        if (!bus)
+                return 0;
+
         assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -1808,7 +1810,9 @@ _public_ int sd_bus_is_open(sd_bus *bus) {
 }
 
 _public_ int sd_bus_is_ready(sd_bus *bus) {
-        assert_return(bus, -EINVAL);
+        if (!bus)
+                return 0;
+
         assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
diff --git a/src/network/networkd-dhcp-common.c b/src/network/networkd-dhcp-common.c
index 0de1892fc9..9677dfb0c3 100644
--- a/src/network/networkd-dhcp-common.c
+++ b/src/network/networkd-dhcp-common.c
@@ -167,7 +167,7 @@ int manager_request_product_uuid(Manager *m, Link *link) {
                         return log_oom();
         }
 
-        if (!m->bus || sd_bus_is_ready(m->bus) <= 0) {
+        if (sd_bus_is_ready(m->bus) <= 0) {
                 log_debug("Not connected to system bus, requesting product UUID later.");
                 return 0;
         }
diff --git a/src/network/networkd-link-bus.c b/src/network/networkd-link-bus.c
index 841d76b461..3311dafd6a 100644
--- a/src/network/networkd-link-bus.c
+++ b/src/network/networkd-link-bus.c
@@ -854,7 +854,7 @@ int link_send_changed_strv(Link *link, char **properties) {
         assert(link->manager);
         assert(properties);
 
-        if (!link->manager->bus || sd_bus_is_ready(link->manager->bus) <= 0)
+        if (sd_bus_is_ready(link->manager->bus) <= 0)
                 return 0;
 
         p = link_bus_path(link);
diff --git a/src/network/networkd-manager-bus.c b/src/network/networkd-manager-bus.c
index a08dff58e7..138d765414 100644
--- a/src/network/networkd-manager-bus.c
+++ b/src/network/networkd-manager-bus.c
@@ -339,7 +339,7 @@ int manager_send_changed_strv(Manager *manager, char **properties) {
         assert(manager);
         assert(properties);
 
-        if (!manager->bus || sd_bus_is_ready(manager->bus) <= 0)
+        if (sd_bus_is_ready(manager->bus) <= 0)
                 return 0;
 
         return sd_bus_emit_properties_changed_strv(
diff --git a/src/network/networkd-manager.c b/src/network/networkd-manager.c
index bfdb1f8c96..a8db2cc44b 100644
--- a/src/network/networkd-manager.c
+++ b/src/network/networkd-manager.c
@@ -767,8 +767,8 @@ int manager_set_hostname(Manager *m, const char *hostname) {
         if (r < 0)
                 return r;
 
-        if (!m->bus || sd_bus_is_ready(m->bus) <= 0) {
-                log_debug("Not connected to system bus, setting hostname later.");
+        if (sd_bus_is_ready(m->bus) <= 0) {
+                log_debug("Not connected to system bus, setting system hostname later.");
                 return 0;
         }
 
@@ -784,7 +784,6 @@ int manager_set_hostname(Manager *m, const char *hostname) {
                         "sb",
                         hostname,
                         false);
-
         if (r < 0)
                 return log_error_errno(r, "Could not set transient hostname: %m");
 
@@ -817,8 +816,8 @@ int manager_set_timezone(Manager *m, const char *tz) {
         if (r < 0)
                 return r;
 
-        if (!m->bus || sd_bus_is_ready(m->bus) <= 0) {
-                log_debug("Not connected to system bus, setting timezone later.");
+        if (sd_bus_is_ready(m->bus) <= 0) {
+                log_debug("Not connected to system bus, setting system timezone later.");
                 return 0;
         }