diff --git a/src/License.cc b/src/License.cc
index 31eb6742..bb208d18 100644
--- a/src/License.cc
+++ b/src/License.cc
@@ -127,6 +127,14 @@ shared_ptr<License> LicenseIndex::get(uint32_t serial_number) const {
   }
 }
 
+shared_ptr<License> LicenseIndex::get_by_bb_username(const string& bb_username) const {
+  try {
+    return this->bb_username_to_license.at(bb_username);
+  } catch (const out_of_range&) {
+    throw missing_license();
+  }
+}
+
 vector<shared_ptr<License>> LicenseIndex::all() const {
   vector<shared_ptr<License>> ret;
   ret.reserve(this->serial_number_to_license.size());
diff --git a/src/License.hh b/src/License.hh
index 0ad0436f..de6a4ad0 100644
--- a/src/License.hh
+++ b/src/License.hh
@@ -100,6 +100,7 @@ public:
 
   size_t count() const;
   std::shared_ptr<License> get(uint32_t serial_number) const;
+  std::shared_ptr<License> get_by_bb_username(const std::string& bb_username) const;
   std::vector<std::shared_ptr<License>> all() const;
 
   void add(std::shared_ptr<License> l);
diff --git a/src/ReceiveCommands.cc b/src/ReceiveCommands.cc
index b15732f1..ce5b9608 100644
--- a/src/ReceiveCommands.cc
+++ b/src/ReceiveCommands.cc
@@ -5003,34 +5003,60 @@ static void on_04_P(shared_ptr<Client> c, uint16_t, uint32_t, string& data) {
   const auto& cmd = check_size_t<C_Login_Patch_04>(data);
   auto s = c->require_server_state();
 
-  try {
-    auto l = s->license_index->verify_bb(cmd.username.decode(), cmd.password.decode());
-    c->set_license(l);
+  string username = cmd.username.decode();
+  string password = cmd.password.decode();
 
-  } catch (const LicenseIndex::incorrect_password& e) {
-    send_message_box(c, string_printf("Login failed: %s", e.what()));
-    c->should_disconnect = true;
-    return;
+  // There are 3 cases here:
+  // - No login information at all: just proceed without checking license
+  // - Username only: check that license exists if allow_unregistered_users is off
+  // - Username and password: call verify_bb
+  if (!username.empty() && !password.empty()) {
+    try {
+      auto l = s->license_index->verify_bb(username, password);
+      c->set_license(l);
 
-  } catch (const LicenseIndex::missing_license& e) {
-    if (!s->allow_unregistered_users) {
+    } catch (const LicenseIndex::incorrect_password& e) {
       send_message_box(c, string_printf("Login failed: %s", e.what()));
       c->should_disconnect = true;
       return;
-    } else {
 
-      auto l = s->license_index->create_license();
-      l->serial_number = fnv1a32(cmd.username.decode()) & 0x7FFFFFFF;
-      l->bb_username = cmd.username.decode();
-      l->bb_password = cmd.password.decode();
-      s->license_index->add(l);
-      if (!s->is_replay) {
-        l->save();
+    } catch (const LicenseIndex::missing_license& e) {
+      if (!s->allow_unregistered_users) {
+        send_message_box(c, string_printf("Login failed: %s", e.what()));
+        c->should_disconnect = true;
+        return;
+      } else {
+
+        auto l = s->license_index->create_license();
+        l->serial_number = fnv1a32(cmd.username.decode()) & 0x7FFFFFFF;
+        l->bb_username = cmd.username.decode();
+        l->bb_password = cmd.password.decode();
+        s->license_index->add(l);
+        if (!s->is_replay) {
+          l->save();
+        }
+        c->set_license(l);
+        string l_str = l->str();
+        c->log.info("Created license %s", l_str.c_str());
       }
-      c->set_license(l);
-      string l_str = l->str();
-      c->log.info("Created license %s", l_str.c_str());
     }
+
+  } else if (!username.empty() && !s->allow_unregistered_users) {
+    try {
+      auto l = s->license_index->get_by_bb_username(username);
+      c->set_license(l);
+    } catch (const LicenseIndex::missing_license& e) {
+      send_message_box(c, string_printf("Login failed: %s", e.what()));
+      c->should_disconnect = true;
+      return;
+    }
+
+  } else {
+    auto l = s->license_index->create_temporary_license();
+    l->serial_number = random_object<uint32_t>() & 0x7FFFFFFF;
+    l->bb_username = "__unknown__";
+    l->bb_password = "__unknown__";
+    c->set_license(l);
   }
 
   // On BB we can use colors and newlines should be \n; on PC we can't use