diff --git a/server/errors.go b/server/errors.go
index 657d1ddc..c6076f3f 100644
--- a/server/errors.go
+++ b/server/errors.go
@@ -122,6 +122,7 @@ var (
 	errHTTPBadRequestTemplateInvalid                 = &errHTTP{40043, http.StatusBadRequest, "invalid request: could not parse template", "https://ntfy.sh/docs/publish/#message-templating", nil}
 	errHTTPBadRequestTemplateDisallowedFunctionCalls = &errHTTP{40044, http.StatusBadRequest, "invalid request: template contains disallowed function calls, e.g. template, call, or define", "https://ntfy.sh/docs/publish/#message-templating", nil}
 	errHTTPBadRequestTemplateExecuteFailed           = &errHTTP{40045, http.StatusBadRequest, "invalid request: template execution failed", "https://ntfy.sh/docs/publish/#message-templating", nil}
+	errHTTPBadRequestInvalidUsername                 = &errHTTP{40046, http.StatusBadRequest, "invalid request: invalid username", "", nil}
 	errHTTPNotFound                                  = &errHTTP{40401, http.StatusNotFound, "page not found", "", nil}
 	errHTTPUnauthorized                              = &errHTTP{40101, http.StatusUnauthorized, "unauthorized", "https://ntfy.sh/docs/publish/#authentication", nil}
 	errHTTPForbidden                                 = &errHTTP{40301, http.StatusForbidden, "forbidden", "https://ntfy.sh/docs/publish/#authentication", nil}
diff --git a/server/server_account.go b/server/server_account.go
index cb841d07..3f2368da 100644
--- a/server/server_account.go
+++ b/server/server_account.go
@@ -2,6 +2,7 @@ package server
 
 import (
 	"encoding/json"
+	"errors"
 	"heckel.io/ntfy/v2/log"
 	"heckel.io/ntfy/v2/user"
 	"heckel.io/ntfy/v2/util"
@@ -37,6 +38,9 @@ func (s *Server) handleAccountCreate(w http.ResponseWriter, r *http.Request, v *
 	}
 	logvr(v, r).Tag(tagAccount).Field("user_name", newAccount.Username).Info("Creating user %s", newAccount.Username)
 	if err := s.userManager.AddUser(newAccount.Username, newAccount.Password, user.RoleUser); err != nil {
+		if errors.Is(err, user.ErrInvalidArgument) {
+			return errHTTPBadRequestInvalidUsername
+		}
 		return err
 	}
 	v.AccountCreated()
diff --git a/user/types.go b/user/types.go
index 68ee02f3..6f6b1f69 100644
--- a/user/types.go
+++ b/user/types.go
@@ -241,7 +241,7 @@ const (
 )
 
 var (
-	allowedUsernameRegex     = regexp.MustCompile(`^[-_.@a-zA-Z0-9]+$`)     // Does not include Everyone (*)
+	allowedUsernameRegex     = regexp.MustCompile(`^[-_.+@a-zA-Z0-9]+$`)    // Does not include Everyone (*)
 	allowedTopicRegex        = regexp.MustCompile(`^[-_A-Za-z0-9]{1,64}$`)  // No '*'
 	allowedTopicPatternRegex = regexp.MustCompile(`^[-_*A-Za-z0-9]{1,64}$`) // Adds '*' for wildcards!
 	allowedTierRegex         = regexp.MustCompile(`^[-_A-Za-z0-9]{1,64}$`)
diff --git a/user/types_test.go b/user/types_test.go
index 811d33f2..690fddf3 100644
--- a/user/types_test.go
+++ b/user/types_test.go
@@ -61,3 +61,15 @@ func TestTierContext(t *testing.T) {
 	require.Equal(t, "price_456", context["stripe_yearly_price_id"])
 
 }
+
+func TestUsernameRegex(t *testing.T) {
+	username := "phil"
+	usernameEmail := "phil@ntfy.sh"
+	usernameEmailAlias := "phil+alias@ntfy.sh"
+	usernameInvalid := "phil\rocks"
+
+	require.True(t, AllowedUsername(username))
+	require.True(t, AllowedUsername(usernameEmail))
+	require.True(t, AllowedUsername(usernameEmailAlias))
+	require.False(t, AllowedUsername(usernameInvalid))
+}