diff --git a/src/conf.c b/src/conf.c
index 2ee632b..1b12c30 100644
--- a/src/conf.c
+++ b/src/conf.c
@@ -558,6 +558,7 @@ static int h_auth(int argc, unsigned char **argv){
 			conf->authfuncs->desc = au->desc;
 			conf->authfuncs->authenticate = au->authenticate;
 			conf->authfuncs->authorize = au->authorize;
+			conf->authfuncs->blocks = au->blocks;
 			break;
 		}
 	  }
diff --git a/src/mainconf.c b/src/mainconf.c
index 7817d8c..14f8c77 100644
--- a/src/mainconf.c
+++ b/src/mainconf.c
@@ -313,8 +313,11 @@ static int srvprepare(struct srvstart *s, int argc, char **argv){
  }
 
  if(conf->authfuncs){
+	struct auth *au;
+
 	srv->authfuncs = copyauth(conf->authfuncs);
 	if(!srv->authfuncs) return 2;
+	for(au = srv->authfuncs; au; au = au->next) if(au->blocks) srv->threadperclient = 1;
  }
 #else
  srv->needuser = 0;
diff --git a/src/plugins/LdapPlugin/ldapauth.c b/src/plugins/LdapPlugin/ldapauth.c
index 0296b21..3d3fc5a 100644
--- a/src/plugins/LdapPlugin/ldapauth.c
+++ b/src/plugins/LdapPlugin/ldapauth.c
@@ -551,6 +551,7 @@ PLUGINAPI int PLUGINCALL start(struct pluginlink * pluginlink,
     myalwaysauth.authenticate = ldapfunc;
     myalwaysauth.authorize = pluginlink->checkACL;
     myalwaysauth.desc = "ldap";
+    myalwaysauth.blocks = 1;
     myalwaysauth.next = pluginlink->authfuncs->next;
     pluginlink->authfuncs->next = &myalwaysauth;
 
diff --git a/src/plugins/PamAuth/pamauth.c b/src/plugins/PamAuth/pamauth.c
index 8ad1069..5b4741a 100644
--- a/src/plugins/PamAuth/pamauth.c
+++ b/src/plugins/PamAuth/pamauth.c
@@ -141,6 +141,7 @@ PLUGINAPI int PLUGINCALL start(struct pluginlink * pluginlink, int argc, unsigne
  pamauth.authenticate = pamfunc;
  pamauth.authorize = pluginlink->checkACL;
  pamauth.desc = "pam";
+ pamauth.blocks = 1;
  pamauth.next = pluginlink->authfuncs->next;
  pluginlink->authfuncs->next = &pamauth;
   
diff --git a/src/plugins/WindowsAuthentication/WindowsAuthentication.c b/src/plugins/WindowsAuthentication/WindowsAuthentication.c
index 2e42636..c398c59 100644
--- a/src/plugins/WindowsAuthentication/WindowsAuthentication.c
+++ b/src/plugins/WindowsAuthentication/WindowsAuthentication.c
@@ -80,6 +80,7 @@ PLUGINAPI int PLUGINCALL WindowsAuthentication(struct pluginlink * pluginlink, i
 		alwaysauth.authenticate = windowsfunc;
 		alwaysauth.authorize = pluginlink->checkACL;
 		alwaysauth.desc = "windows";
+		alwaysauth.blocks = 1;
 		alwaysauth.next = pluginlink->authfuncs->next;
 		pluginlink->authfuncs->next = &alwaysauth;
 		loaded = 1;
diff --git a/src/structures.h b/src/structures.h
index 3289693..7b8123e 100644
--- a/src/structures.h
+++ b/src/structures.h
@@ -284,6 +284,7 @@ struct auth {
 	AUTHFUNC authenticate;
 	AUTHFUNC authorize;
 	char * desc;
+	int blocks;	/* waits other than in sockpoll(): PAM, LDAP */
 };
 
 struct iplist {