diff --git a/os/client.c b/os/client.c
index c844eb6d86..44d2a070a0 100644
--- a/os/client.c
+++ b/os/client.c
@@ -107,7 +107,7 @@ DetermineClientPid(struct _Client * client)
     LocalClientCredRec *lcc = NULL;
     pid_t pid = -1;
 
-    if (client == NullClient)
+    if (client == NULL)
         return pid;
 
     if (client == serverClient)
@@ -451,7 +451,7 @@ void
 ReserveClientIds(struct _Client *client)
 {
 #ifdef CLIENTIDS
-    if (client == NullClient)
+    if (client == NULL)
         return;
 
     assert(!client->clientIds);
@@ -483,7 +483,7 @@ void
 ReleaseClientIds(struct _Client *client)
 {
 #ifdef CLIENTIDS
-    if (client == NullClient)
+    if (client == NULL)
         return;
 
     if (!client->clientIds)
@@ -518,7 +518,7 @@ ReleaseClientIds(struct _Client *client)
 pid_t
 GetClientPid(struct _Client *client)
 {
-    if (client == NullClient)
+    if (client == NULL)
         return -1;
 
     if (!client->clientIds)
@@ -544,7 +544,7 @@ GetClientPid(struct _Client *client)
 const char *
 GetClientCmdName(struct _Client *client)
 {
-    if (client == NullClient)
+    if (client == NULL)
         return NULL;
 
     if (!client->clientIds)
@@ -570,7 +570,7 @@ GetClientCmdName(struct _Client *client)
 const char *
 GetClientCmdArgs(struct _Client *client)
 {
-    if (client == NullClient)
+    if (client == NULL)
         return NULL;
 
     if (!client->clientIds)
diff --git a/os/connection.c b/os/connection.c
index 9864c6142e..c827047208 100644
--- a/os/connection.c
+++ b/os/connection.c
@@ -626,7 +626,7 @@ AllocNewConnection(XtransConnInfo trans_conn, int fd, CARD32 conn_time)
 
     OsCommPtr oc = calloc(1, sizeof(OsCommRec));
     if (!oc)
-        return NullClient;
+        return NULL;
     oc->trans_conn = trans_conn;
     oc->fd = fd;
     oc->input = (ConnectionInputPtr) NULL;
@@ -636,7 +636,7 @@ AllocNewConnection(XtransConnInfo trans_conn, int fd, CARD32 conn_time)
     oc->flags = 0;
     if (!(client = NextAvailableClient((void *) oc))) {
         free(oc);
-        return NullClient;
+        return NULL;
     }
     client->local = ComputeLocalClient(client);
     ospoll_add(server_poll, fd,