diff --git a/src/newgrf_internal.h b/src/newgrf_internal.h
index 2121263f72..b4ada3532d 100644
--- a/src/newgrf_internal.h
+++ b/src/newgrf_internal.h
@@ -284,6 +284,20 @@ struct VarAction2AdjustInfo {
 	uint8_t varsize;
 };
 
+struct DeterministicSpriteGroupShadowCopy {
+	std::vector<DeterministicSpriteGroupAdjust> adjusts;
+	std::vector<DeterministicSpriteGroupRange> ranges;
+	const SpriteGroup *default_group;
+	bool calculated_result;
+};
+
+struct RandomizedSpriteGroupShadowCopy {
+	std::vector<const SpriteGroup *> groups;
+};
+
+extern robin_hood::unordered_node_map<const DeterministicSpriteGroup *, DeterministicSpriteGroupShadowCopy> _deterministic_sg_shadows;
+extern robin_hood::unordered_flat_map<const RandomizedSpriteGroup *, RandomizedSpriteGroupShadowCopy> _randomized_sg_shadows;
+
 const SpriteGroup *PruneTargetSpriteGroup(const SpriteGroup *result);
 void OptimiseVarAction2Adjust(VarAction2OptimiseState &state, const VarAction2AdjustInfo info, DeterministicSpriteGroup *group, DeterministicSpriteGroupAdjust &adjust);
 void OptimiseVarAction2DeterministicSpriteGroup(VarAction2OptimiseState &state, const VarAction2AdjustInfo info, DeterministicSpriteGroup *group, std::vector<DeterministicSpriteGroupAdjust> &saved_adjusts);
diff --git a/src/newgrf_spritegroup.cpp b/src/newgrf_spritegroup.cpp
index f385d5805b..1c46180f01 100644
--- a/src/newgrf_spritegroup.cpp
+++ b/src/newgrf_spritegroup.cpp
@@ -10,6 +10,7 @@
 #include "stdafx.h"
 #include "debug.h"
 #include "newgrf_spritegroup.h"
+#include "newgrf_internal.h"
 #include "newgrf_profiling.h"
 #include "core/pool_func.hpp"
 #include "vehicle_type.h"
diff --git a/src/newgrf_spritegroup.h b/src/newgrf_spritegroup.h
index 1d663f9ce9..a5d0056bd0 100644
--- a/src/newgrf_spritegroup.h
+++ b/src/newgrf_spritegroup.h
@@ -483,13 +483,6 @@ enum DeterministicSpriteGroupFlags : uint8_t {
 };
 DECLARE_ENUM_AS_BIT_SET(DeterministicSpriteGroupFlags)
 
-struct DeterministicSpriteGroupShadowCopy {
-	std::vector<DeterministicSpriteGroupAdjust> adjusts;
-	std::vector<DeterministicSpriteGroupRange> ranges;
-	const SpriteGroup *default_group;
-	bool calculated_result;
-};
-
 struct DeterministicSpriteGroup : SpriteGroup {
 	DeterministicSpriteGroup() : SpriteGroup(SGT_DETERMINISTIC) {}
 
@@ -518,10 +511,6 @@ enum RandomizedSpriteGroupCompareMode : uint8_t {
 	RSG_CMP_ALL,
 };
 
-struct RandomizedSpriteGroupShadowCopy {
-	std::vector<const SpriteGroup *> groups;
-};
-
 struct RandomizedSpriteGroup : SpriteGroup {
 	RandomizedSpriteGroup() : SpriteGroup(SGT_RANDOMIZED) {}
 
@@ -541,8 +530,6 @@ protected:
 	const SpriteGroup *Resolve(ResolverObject &object) const override;
 };
 
-extern robin_hood::unordered_node_map<const DeterministicSpriteGroup *, DeterministicSpriteGroupShadowCopy> _deterministic_sg_shadows;
-extern robin_hood::unordered_flat_map<const RandomizedSpriteGroup *, RandomizedSpriteGroupShadowCopy> _randomized_sg_shadows;
 extern bool _grfs_loaded_with_sg_shadow_enable;
 
 /* This contains a callback result. A failed callback has a value of