diff --git a/src/engine/shared/datafile.cpp b/src/engine/shared/datafile.cpp
index c0f668487..c0c08c5dc 100644
--- a/src/engine/shared/datafile.cpp
+++ b/src/engine/shared/datafile.cpp
@@ -611,7 +611,7 @@ int CDataFileWriter::GetExtendedItemTypeIndex(int Type)
 	return Index;
 }
 
-int CDataFileWriter::AddItem(int Type, int ID, int Size, void *pData)
+int CDataFileWriter::AddItem(int Type, int ID, int Size, const void *pData)
 {
 	dbg_assert((Type >= 0 && Type < MAX_ITEM_TYPES) || Type >= OFFSET_UUID, "incorrect type");
 	dbg_assert(m_NumItems < 1024, "too many items");
@@ -650,7 +650,7 @@ int CDataFileWriter::AddItem(int Type, int ID, int Size, void *pData)
 	return m_NumItems - 1;
 }
 
-int CDataFileWriter::AddData(int Size, void *pData, int CompressionLevel)
+int CDataFileWriter::AddData(int Size, const void *pData, int CompressionLevel)
 {
 	dbg_assert(m_NumDatas < 1024, "too much data");
 
@@ -666,7 +666,7 @@ int CDataFileWriter::AddData(int Size, void *pData, int CompressionLevel)
 	return m_NumDatas - 1;
 }
 
-int CDataFileWriter::AddDataSwapped(int Size, void *pData)
+int CDataFileWriter::AddDataSwapped(int Size, const void *pData)
 {
 	dbg_assert(Size % sizeof(int) == 0, "incorrect boundary");
 
diff --git a/src/engine/shared/datafile.h b/src/engine/shared/datafile.h
index abc5af217..c55f1fccf 100644
--- a/src/engine/shared/datafile.h
+++ b/src/engine/shared/datafile.h
@@ -126,9 +126,9 @@ public:
 	void Init();
 	bool OpenFile(class IStorage *pStorage, const char *pFilename, int StorageType = IStorage::TYPE_SAVE);
 	bool Open(class IStorage *pStorage, const char *pFilename, int StorageType = IStorage::TYPE_SAVE);
-	int AddData(int Size, void *pData, int CompressionLevel = Z_DEFAULT_COMPRESSION);
-	int AddDataSwapped(int Size, void *pData);
-	int AddItem(int Type, int ID, int Size, void *pData);
+	int AddData(int Size, const void *pData, int CompressionLevel = Z_DEFAULT_COMPRESSION);
+	int AddDataSwapped(int Size, const void *pData);
+	int AddItem(int Type, int ID, int Size, const void *pData);
 	void Finish();
 };
 
diff --git a/src/game/editor/io.cpp b/src/game/editor/io.cpp
index f7ea4dac9..bf7539111 100644
--- a/src/game/editor/io.cpp
+++ b/src/game/editor/io.cpp
@@ -192,7 +192,7 @@ bool CEditorMap::Save(const char *pFileName)
 		GItemEx.m_Version = CMapItemGroupEx::CURRENT_VERSION;
 		GItemEx.m_ParallaxZoom = pGroup->m_ParallaxZoom;
 
-		for(const auto &pLayer : pGroup->m_vpLayers)
+		for(CLayer *pLayer : pGroup->m_vpLayers)
 		{
 			if(pLayer->m_Type == LAYERTYPE_TILES)
 			{
diff --git a/src/game/server/gamecontext.cpp b/src/game/server/gamecontext.cpp
index e2b92ccbc..c95ab3407 100644
--- a/src/game/server/gamecontext.cpp
+++ b/src/game/server/gamecontext.cpp
@@ -3785,7 +3785,7 @@ void CGameContext::OnMapChange(char *pNewMapName, int MapNameSize)
 			Writer.AddData(TotalLength, pSettings);
 			continue;
 		}
-		unsigned char *pData = (unsigned char *)Reader.GetData(i);
+		const void *pData = Reader.GetData(i);
 		int Size = Reader.GetDataSize(i);
 		Writer.AddData(Size, pData);
 		Reader.UnloadData(i);
diff --git a/src/tools/map_resave.cpp b/src/tools/map_resave.cpp
index fbb65b482..1f6698828 100644
--- a/src/tools/map_resave.cpp
+++ b/src/tools/map_resave.cpp
@@ -24,7 +24,7 @@ int main(int argc, const char **argv)
 	for(int Index = 0; Index < Reader.NumItems(); Index++)
 	{
 		int Type, ID;
-		void *pPtr = Reader.GetItem(Index, &Type, &ID);
+		const void *pPtr = Reader.GetItem(Index, &Type, &ID);
 
 		// filter ITEMTYPE_EX items, they will be automatically added again
 		if(Type == ITEMTYPE_EX)
@@ -37,7 +37,7 @@ int main(int argc, const char **argv)
 	// add all data
 	for(int Index = 0; Index < Reader.NumData(); Index++)
 	{
-		void *pPtr = Reader.GetData(Index);
+		const void *pPtr = Reader.GetData(Index);
 		int Size = Reader.GetDataSize(Index);
 		Writer.AddData(Size, pPtr);
 	}