diff --git a/server/errors.go b/server/errors.go
index 5498d12f..c6076f3f 100644
--- a/server/errors.go
+++ b/server/errors.go
@@ -122,7 +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}
-	errHTTPBadRequestInvalidArgument                 = &errHTTP{40046, http.StatusBadRequest, "invalid request: invalid argument", "", 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 31d581f1..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"
@@ -37,11 +38,10 @@ 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 err.Error() == "invalid argument" {
-			return errHTTPBadRequestInvalidArgument
-		} else {
-			return err
+		if errors.Is(err, user.ErrInvalidArgument) {
+			return errHTTPBadRequestInvalidUsername
 		}
+		return err
 	}
 	v.AccountCreated()
 	return s.writeJSON(w, newSuccessResponse())