diff --git a/src/company_gui.cpp b/src/company_gui.cpp
index 9b9bd46c30..0c5ea96194 100644
--- a/src/company_gui.cpp
+++ b/src/company_gui.cpp
@@ -1017,7 +1017,7 @@ public:
 			}
 		} else {
 			/* Setting group livery */
-			Command<CMD_SET_GROUP_LIVERY>::Post(this->sel, widget == WID_SCL_PRI_COL_DROPDOWN, colour);
+			Command<CMD_SET_GROUP_LIVERY>::Post(static_cast<GroupID>(this->sel), widget == WID_SCL_PRI_COL_DROPDOWN, colour);
 		}
 	}
 
diff --git a/src/group.h b/src/group.h
index 5b74b8c655..4259e074bc 100644
--- a/src/group.h
+++ b/src/group.h
@@ -17,7 +17,7 @@
 #include "engine_type.h"
 #include "livery.h"
 
-typedef Pool<Group, GroupID, 16, 64000> GroupPool;
+typedef Pool<Group, GroupID, 16, GROUP_END> GroupPool;
 extern GroupPool _group_pool; ///< Pool of groups.
 
 /** Statistics and caches on the vehicles in a group. */
diff --git a/src/group_gui.cpp b/src/group_gui.cpp
index 14a8ae4605..3d2fc6b651 100644
--- a/src/group_gui.cpp
+++ b/src/group_gui.cpp
@@ -986,7 +986,7 @@ public:
 
 	void OnQueryTextFinished(std::optional<std::string> str) override
 	{
-		if (str.has_value()) Command<CMD_ALTER_GROUP>::Post(STR_ERROR_GROUP_CAN_T_RENAME, AlterGroupMode::Rename, this->group_rename, 0, *str);
+		if (str.has_value()) Command<CMD_ALTER_GROUP>::Post(STR_ERROR_GROUP_CAN_T_RENAME, AlterGroupMode::Rename, this->group_rename, INVALID_GROUP, *str);
 		this->group_rename = INVALID_GROUP;
 	}
 
diff --git a/src/group_type.h b/src/group_type.h
index 32c4926197..e7f75af3d5 100644
--- a/src/group_type.h
+++ b/src/group_type.h
@@ -10,12 +10,14 @@
 #ifndef GROUP_TYPE_H
 #define GROUP_TYPE_H
 
-typedef uint16_t GroupID; ///< Type for all group identifiers.
-
-static const GroupID NEW_GROUP     = 0xFFFC; ///< Sentinel for a to-be-created group.
-static const GroupID ALL_GROUP     = 0xFFFD; ///< All vehicles are in this group.
-static const GroupID DEFAULT_GROUP = 0xFFFE; ///< Ungrouped vehicles are in this group.
-static const GroupID INVALID_GROUP = 0xFFFF; ///< Sentinel for invalid groups.
+enum GroupID : uint16_t {
+	GROUP_BEGIN = 0,
+	GROUP_END = 64000,
+	NEW_GROUP = 0xFFFC, ///< Sentinel for a to-be-created group.
+	ALL_GROUP = 0xFFFD, ///< All vehicles are in this group.
+	DEFAULT_GROUP = 0xFFFE, ///< Ungrouped vehicles are in this group.
+	INVALID_GROUP = 0xFFFF ///< Sentinel for invalid groups.
+};
 
 static const uint MAX_LENGTH_GROUP_NAME_CHARS = 32; ///< The maximum length of a group name in characters including '\0'
 
diff --git a/src/script/api/script_group.cpp b/src/script/api/script_group.cpp
index 5c50713d55..818f9d150c 100644
--- a/src/script/api/script_group.cpp
+++ b/src/script/api/script_group.cpp
@@ -36,7 +36,7 @@
 	if (!ScriptObject::Command<CMD_CREATE_GROUP>::Do(&ScriptInstance::DoCommandReturnGroupID, (::VehicleType)vehicle_type, parent_group_id)) return GROUP_INVALID;
 
 	/* In case of test-mode, we return GroupID 0 */
-	return static_cast<GroupID>(0);
+	return ::GROUP_BEGIN;
 }
 
 /* static */ bool ScriptGroup::DeleteGroup(GroupID group_id)
@@ -65,7 +65,7 @@
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_GROUP_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
 
-	return ScriptObject::Command<CMD_ALTER_GROUP>::Do(AlterGroupMode::Rename, group_id, 0, text);
+	return ScriptObject::Command<CMD_ALTER_GROUP>::Do(AlterGroupMode::Rename, group_id, ::INVALID_GROUP, text);
 }
 
 /* static */ std::optional<std::string> ScriptGroup::GetName(GroupID group_id)