diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 8d1acfb988..6be30415e8 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -5689,14 +5689,14 @@ static const CallbackResultSpriteGroup *NewCallbackResultSpriteGroup(uint16 grou
 
 /* Helper function to either create a callback or link to a previously
  * defined spritegroup. */
-static const SpriteGroup *GetGroupFromGroupID(byte setid, byte type, uint16 groupid)
+static const SpriteGroup *GetGroupFromGroupID(uint16 setid, byte type, uint16 groupid)
 {
 	if (HasBit(groupid, 15)) {
 		return NewCallbackResultSpriteGroup(groupid);
 	}
 
-	if (groupid > MAX_SPRITEGROUP || _cur.spritegroups[groupid] == nullptr) {
-		grfmsg(1, "GetGroupFromGroupID(0x%02X:0x%02X): Groupid 0x%04X does not exist, leaving empty", setid, type, groupid);
+	if ((size_t)groupid >= _cur.spritegroups.size() || _cur.spritegroups[groupid] == nullptr) {
+		grfmsg(1, "GetGroupFromGroupID(0x%04X:0x%02X): Groupid 0x%04X does not exist, leaving empty", setid, type, groupid);
 		return nullptr;
 	}
 
@@ -5707,6 +5707,8 @@ static const SpriteGroup *GetGroupFromGroupID(byte setid, byte type, uint16 grou
 
 static const SpriteGroup *GetGroupByID(uint16 groupid)
 {
+	if ((size_t)groupid >= _cur.spritegroups.size()) return nullptr;
+
 	const SpriteGroup *result = _cur.spritegroups[groupid];
 	return result;
 }
@@ -5719,14 +5721,14 @@ static const SpriteGroup *GetGroupByID(uint16 groupid)
  * @param spriteid Raw value from the GRF for the new spritegroup; describes either the return value or the referenced spritegroup.
  * @return Created spritegroup.
  */
-static const SpriteGroup *CreateGroupFromGroupID(byte feature, byte setid, byte type, uint16 spriteid)
+static const SpriteGroup *CreateGroupFromGroupID(byte feature, uint16 setid, byte type, uint16 spriteid)
 {
 	if (HasBit(spriteid, 15)) {
 		return NewCallbackResultSpriteGroup(spriteid);
 	}
 
 	if (!_cur.IsValidSpriteSet(feature, spriteid)) {
-		grfmsg(1, "CreateGroupFromGroupID(0x%02X:0x%02X): Sprite set %u invalid", setid, type, spriteid);
+		grfmsg(1, "CreateGroupFromGroupID(0x%04X:0x%02X): Sprite set %u invalid", setid, type, spriteid);
 		return nullptr;
 	}
 
@@ -5787,6 +5789,7 @@ static void NewSpriteGroup(ByteReader *buf)
 	 *
 	 * B feature       see action 1
 	 * B set-id        ID of this particular definition
+	 *                 This is an extended byte if feature "more_action2_ids" is tested for
 	 * B type/num-entries
 	 *                 if 80 or greater, this is a randomized or variational
 	 *                 list definition, see below
@@ -5802,7 +5805,7 @@ static void NewSpriteGroup(ByteReader *buf)
 		return;
 	}
 
-	uint8 setid   = buf->ReadByte();
+	uint16 setid  = HasBit(_cur.grffile->observed_feature_tests, GFTOF_MORE_ACTION2_IDS) ? buf->ReadExtendedByte() : buf->ReadByte();
 	uint8 type    = buf->ReadByte();
 
 	/* Sprite Groups are created here but they are allocated from a pool, so
@@ -6188,6 +6191,7 @@ static void NewSpriteGroup(ByteReader *buf)
 		}
 	}
 
+	if ((size_t)setid >= _cur.spritegroups.size()) _cur.spritegroups.resize(setid + 1);
 	_cur.spritegroups[setid] = act_group;
 }
 
@@ -6250,7 +6254,7 @@ static CargoID TranslateCargo(uint8 feature, uint8 ctype)
 
 static bool IsValidGroupID(uint16 groupid, const char *function)
 {
-	if (groupid > MAX_SPRITEGROUP || _cur.spritegroups[groupid] == nullptr) {
+	if ((size_t)groupid >= _cur.spritegroups.size() || _cur.spritegroups[groupid] == nullptr) {
 		grfmsg(1, "%s: Spritegroup 0x%04X out of range or empty, skipping.", function, groupid);
 		return false;
 	}
diff --git a/src/newgrf_extension.cpp b/src/newgrf_extension.cpp
index 45af5f5d2b..8794260218 100644
--- a/src/newgrf_extension.cpp
+++ b/src/newgrf_extension.cpp
@@ -61,6 +61,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("road_stops", 7),
 	GRFFeatureInfo("new_landscape", 2),
 	GRFFeatureInfo("more_objects_per_grf", 1, GFTOF_MORE_OBJECTS_PER_GRF),
+	GRFFeatureInfo("more_action2_ids", 1, GFTOF_MORE_ACTION2_IDS),
 	GRFFeatureInfo(),
 };
 
diff --git a/src/newgrf_extension.h b/src/newgrf_extension.h
index d06beb050f..9cc6705473 100644
--- a/src/newgrf_extension.h
+++ b/src/newgrf_extension.h
@@ -91,6 +91,7 @@ enum Action2VariableRemapIds {
 
 enum GRFFeatureTestObservationFlag : uint8 {
 	GFTOF_MORE_OBJECTS_PER_GRF = 0,
+	GFTOF_MORE_ACTION2_IDS,
 
 	GFTOF_INVALID = 0xFF,
 };
diff --git a/src/newgrf_internal.h b/src/newgrf_internal.h
index 1dca36dad3..da18417dd1 100644
--- a/src/newgrf_internal.h
+++ b/src/newgrf_internal.h
@@ -20,8 +20,6 @@
 #include "3rdparty/cpp-btree/btree_map.h"
 #include <bitset>
 
-static const uint MAX_SPRITEGROUP = UINT8_MAX; ///< Maximum GRF-local ID for a spritegroup.
-
 /** Base GRF ID for OpenTTD's base graphics GRFs. */
 static const uint32 OPENTTD_GRAPHICS_BASE_GRF_ID = BSWAP32(0xFF4F5400);
 
@@ -66,7 +64,7 @@ public:
 	int skip_sprites;         ///< Number of pseudo sprites to skip before processing the next one. (-1 to skip to end of file)
 
 	/* Currently referenceable spritegroups */
-	const SpriteGroup *spritegroups[MAX_SPRITEGROUP + 1];
+	std::vector<const SpriteGroup *> spritegroups;
 
 	/* VarAction2 temporary storage variable tracking */
 	btree::btree_map<const SpriteGroup *, VarAction2GroupVariableTracking *> group_temp_store_variable_tracking;
@@ -124,7 +122,7 @@ public:
 			this->spritesets[i].clear();
 		}
 
-		memset(this->spritegroups, 0, sizeof(this->spritegroups));
+		this->spritegroups.clear();
 
 		this->group_temp_store_variable_tracking.clear();
 		this->group_temp_store_variable_tracking_storage.EmptyArena();