diff --git a/src/script/api/script_sign.cpp b/src/script/api/script_sign.cpp
index 275d4300b0..8d9d364069 100644
--- a/src/script/api/script_sign.cpp
+++ b/src/script/api/script_sign.cpp
@@ -84,5 +84,5 @@
 	if (!ScriptObject::Command<CMD_PLACE_SIGN>::Do(&ScriptInstance::DoCommandReturnSignID, location, text)) return INVALID_SIGN;
 
 	/* In case of test-mode, we return SignID 0 */
-	return 0;
+	return ::SIGN_BEGIN;
 }
diff --git a/src/signs_base.h b/src/signs_base.h
index 718ffac320..5775d7a90a 100644
--- a/src/signs_base.h
+++ b/src/signs_base.h
@@ -15,7 +15,7 @@
 #include "core/pool_type.hpp"
 #include "company_type.h"
 
-typedef Pool<Sign, SignID, 16, 64000> SignPool;
+typedef Pool<Sign, SignID, 16, SIGN_END> SignPool;
 extern SignPool _sign_pool;
 
 struct Sign : SignPool::PoolItem<&_sign_pool> {
diff --git a/src/signs_type.h b/src/signs_type.h
index 5dec4a560e..f7243b8c1f 100644
--- a/src/signs_type.h
+++ b/src/signs_type.h
@@ -11,10 +11,13 @@
 #define SIGNS_TYPE_H
 
 /** The type of the IDs of signs. */
-typedef uint16_t SignID;
-struct Sign;
+enum SignID : uint16_t {
+	SIGN_BEGIN = 0,
+	SIGN_END = 64000,
+	INVALID_SIGN = 0xFFFF ///< Sentinel for an invalid sign.
+};
 
-static const SignID INVALID_SIGN = 0xFFFF; ///< Sentinel for an invalid sign.
+struct Sign;
 
 static const uint MAX_LENGTH_SIGN_NAME_CHARS = 32; ///< The maximum length of a sign name in characters including '\0'