diff --git a/Source/mpq/mpq_reader.cpp b/Source/mpq/mpq_reader.cpp
index 3f2144182..d02652a78 100644
--- a/Source/mpq/mpq_reader.cpp
+++ b/Source/mpq/mpq_reader.cpp
@@ -96,7 +96,7 @@ std::unique_ptr<std::byte[]> MpqArchive::ReadFile(std::string_view filename, std
 	return result;
 }
 
-int32_t MpqArchive::ReadBlock(uint32_t fileNumber, uint32_t blockNumber, uint8_t *out, uint32_t outSize)
+int32_t MpqArchive::ReadBlock(uint32_t fileNumber, uint32_t blockNumber, uint8_t *out, size_t outSize)
 {
 	std::vector<std::uint8_t> &tmpBuf = GetTemporaryBuffer(outSize);
 	return libmpq__block_read_with_temporary_buffer(
diff --git a/Source/mpq/mpq_reader.hpp b/Source/mpq/mpq_reader.hpp
index 7a359fb40..eb6fa46d0 100644
--- a/Source/mpq/mpq_reader.hpp
+++ b/Source/mpq/mpq_reader.hpp
@@ -44,7 +44,7 @@ public:
 	std::unique_ptr<std::byte[]> ReadFile(std::string_view filename, std::size_t &fileSize, int32_t &error);
 
 	// Returns error code.
-	int32_t ReadBlock(uint32_t fileNumber, uint32_t blockNumber, uint8_t *out, uint32_t outSize);
+	int32_t ReadBlock(uint32_t fileNumber, uint32_t blockNumber, uint8_t *out, size_t outSize);
 
 	std::size_t GetUnpackedFileSize(uint32_t fileNumber, int32_t &error);
 
diff --git a/Source/mpq/mpq_sdl_rwops.cpp b/Source/mpq/mpq_sdl_rwops.cpp
index b360953c6..a49a04f8e 100644
--- a/Source/mpq/mpq_sdl_rwops.cpp
+++ b/Source/mpq/mpq_sdl_rwops.cpp
@@ -15,13 +15,13 @@ struct Data {
 	std::optional<MpqArchive> ownedArchive;
 	MpqArchive *mpqArchive;
 	uint32_t fileNumber;
-	uint32_t blockSize;
-	uint32_t lastBlockSize;
+	size_t blockSize;
+	size_t lastBlockSize;
 	uint32_t numBlocks;
-	uint32_t size;
+	size_t size;
 
 	// State:
-	uint32_t position;
+	size_t position;
 	bool blockRead;
 	std::unique_ptr<uint8_t[]> blockData;
 };
@@ -56,25 +56,25 @@ static Sint64 MpqFileRwSize(struct SDL_RWops *context)
 static OffsetType MpqFileRwSeek(struct SDL_RWops *context, OffsetType offset, int whence)
 {
 	Data &data = *GetData(context);
-	OffsetType newPosition;
+	size_t newPosition;
 	switch (whence) {
 	case RW_SEEK_SET:
-		newPosition = offset;
+		newPosition = static_cast<size_t>(offset);
 		break;
 	case RW_SEEK_CUR:
-		newPosition = data.position + offset;
+		newPosition = static_cast<size_t>(data.position + offset);
 		break;
 	case RW_SEEK_END:
-		newPosition = data.size + offset;
+		newPosition = static_cast<size_t>(data.size + offset);
 		break;
 	default:
 		return -1;
 	}
 
-	if (newPosition == static_cast<OffsetType>(data.position))
-		return newPosition;
+	if (newPosition == data.position)
+		return static_cast<OffsetType>(newPosition);
 
-	if (newPosition > static_cast<OffsetType>(data.size)) {
+	if (newPosition > data.size) {
 		SDL_SetError("MpqFileRwSeek beyond EOF (%d > %u)", static_cast<int>(newPosition), data.size);
 		return -1;
 	}
@@ -89,14 +89,14 @@ static OffsetType MpqFileRwSeek(struct SDL_RWops *context, OffsetType offset, in
 
 	data.position = newPosition;
 
-	return newPosition;
+	return static_cast<OffsetType>(newPosition);
 }
 
 static SizeType MpqFileRwRead(struct SDL_RWops *context, void *ptr, SizeType size, SizeType maxnum)
 {
 	Data &data = *GetData(context);
-	const SizeType totalSize = size * maxnum;
-	uint32_t remainingSize = totalSize;
+	const size_t totalSize = size * maxnum;
+	size_t remainingSize = totalSize;
 
 	auto *out = static_cast<uint8_t *>(ptr);
 
@@ -104,13 +104,13 @@ static SizeType MpqFileRwRead(struct SDL_RWops *context, void *ptr, SizeType siz
 		data.blockData = std::unique_ptr<uint8_t[]> { new uint8_t[data.blockSize] };
 	}
 
-	uint32_t blockNumber = data.position / data.blockSize;
+	uint32_t blockNumber = static_cast<uint32_t>(data.position / data.blockSize);
 	while (remainingSize > 0) {
 		if (data.position == data.size) {
 			break;
 		}
 
-		const uint32_t currentBlockSize = blockNumber + 1 == data.numBlocks ? data.lastBlockSize : data.blockSize;
+		const size_t currentBlockSize = blockNumber + 1 == data.numBlocks ? data.lastBlockSize : data.blockSize;
 
 		if (!data.blockRead) {
 			const int32_t error = data.mpqArchive->ReadBlock(data.fileNumber, blockNumber, data.blockData.get(), currentBlockSize);
@@ -121,8 +121,8 @@ static SizeType MpqFileRwRead(struct SDL_RWops *context, void *ptr, SizeType siz
 			data.blockRead = true;
 		}
 
-		const uint32_t blockPosition = data.position - blockNumber * data.blockSize;
-		const uint32_t remainingBlockSize = currentBlockSize - blockPosition;
+		const size_t blockPosition = data.position - blockNumber * data.blockSize;
+		const size_t remainingBlockSize = currentBlockSize - blockPosition;
 
 		if (remainingSize < remainingBlockSize) {
 			std::memcpy(out, data.blockData.get() + blockPosition, remainingSize);
@@ -138,7 +138,7 @@ static SizeType MpqFileRwRead(struct SDL_RWops *context, void *ptr, SizeType siz
 		data.blockRead = false;
 	}
 
-	return (totalSize - remainingSize) / size;
+	return static_cast<SizeType>((totalSize - remainingSize) / size);
 }
 
 static int MpqFileRwClose(struct SDL_RWops *context)
@@ -206,7 +206,7 @@ SDL_RWops *SDL_RWops_FromMpqFile(MpqArchive &mpqArchive, uint32_t fileNumber, st
 	}
 	data->numBlocks = numBlocks;
 
-	const std::uint32_t blockSize = archive.GetBlockSize(fileNumber, 0, error);
+	const size_t blockSize = archive.GetBlockSize(fileNumber, 0, error);
 	if (error != 0) {
 		SDL_SetError("MpqFileRwRead GetBlockSize: %s", MpqArchive::ErrorMessage(error));
 		return nullptr;