diff --git a/Source/Core/DiscIO/CISOBlob.cpp b/Source/Core/DiscIO/CISOBlob.cpp
index aaffe0e608..5070c8e796 100644
--- a/Source/Core/DiscIO/CISOBlob.cpp
+++ b/Source/Core/DiscIO/CISOBlob.cpp
@@ -53,14 +53,14 @@ bool CISOFileReader::Read(u64 offset, u64 nbytes, u8* out_ptr)
 {
 	while (nbytes != 0)
 	{
-		auto const block = offset / m_block_size;
-		auto const data_offset = offset % m_block_size;
+		u64 const block = offset / m_block_size;
+		u64 const data_offset = offset % m_block_size;
+		u64 const bytes_to_read = std::min(m_block_size - data_offset, nbytes);
 
-		auto const bytes_to_read = std::min(m_block_size - data_offset, nbytes);
 		if (block < CISO_MAP_SIZE && UNUSED_BLOCK_ID != m_ciso_map[block])
 		{
 			// calculate the base address
-			auto const file_off = CISO_HEADER_SIZE + m_ciso_map[block] * (u64)m_block_size + data_offset;
+			u64 const file_off = CISO_HEADER_SIZE + m_ciso_map[block] * (u64)m_block_size + data_offset;
 
 			if (!(m_file.Seek(file_off, SEEK_SET) && m_file.ReadArray(out_ptr, bytes_to_read)))
 				return false;