diff --git a/AUTHORS b/AUTHORS
index 15eec14f9..29184c6fe 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -102,6 +102,7 @@ Sandro Rodrigues
 Shaheed Haque
 Shaun Stanworth
 Silvano Cerza
+Simon Charette
 Sora Yanai
 Spencer Carroll
 Stéphane Raimbault
diff --git a/oauth2_provider/admin.py b/oauth2_provider/admin.py
index cefc75bb6..f3e98ac19 100644
--- a/oauth2_provider/admin.py
+++ b/oauth2_provider/admin.py
@@ -15,7 +15,7 @@
 )
 
 
-has_email = hasattr(get_user_model(), "email")
+username_field = get_user_model().USERNAME_FIELD
 
 
 class ApplicationAdmin(admin.ModelAdmin):
@@ -25,7 +25,7 @@ class ApplicationAdmin(admin.ModelAdmin):
         "client_type": admin.HORIZONTAL,
         "authorization_grant_type": admin.VERTICAL,
     }
-    search_fields = ("name",) + (("user__email",) if has_email else ())
+    search_fields = ("name", f"user__{username_field}")
     raw_id_fields = ("user",)
 
 
@@ -33,20 +33,20 @@ class AccessTokenAdmin(admin.ModelAdmin):
     list_display = ("token", "user", "application", "expires")
     list_select_related = ("application", "user")
     raw_id_fields = ("user", "source_refresh_token")
-    search_fields = ("token",) + (("user__email",) if has_email else ())
+    search_fields = ("token", f"user__{username_field}")
     list_filter = ("application",)
 
 
 class GrantAdmin(admin.ModelAdmin):
     list_display = ("code", "application", "user", "expires")
     raw_id_fields = ("user",)
-    search_fields = ("code",) + (("user__email",) if has_email else ())
+    search_fields = ("code", f"user__{username_field}")
 
 
 class IDTokenAdmin(admin.ModelAdmin):
     list_display = ("jti", "user", "application", "expires")
     raw_id_fields = ("user",)
-    search_fields = ("user__email",) if has_email else ()
+    search_fields = ("user__email", f"user__{username_field}")
     list_filter = ("application",)
     list_select_related = ("application", "user")
 
@@ -54,7 +54,7 @@ class IDTokenAdmin(admin.ModelAdmin):
 class RefreshTokenAdmin(admin.ModelAdmin):
     list_display = ("token", "user", "application")
     raw_id_fields = ("user", "access_token")
-    search_fields = ("token",) + (("user__email",) if has_email else ())
+    search_fields = ("token", f"user__{username_field}")
     list_filter = ("application",)