diff --git a/repak/src/data.rs b/repak/src/data.rs
index cb71aac..37a3cac 100644
--- a/repak/src/data.rs
+++ b/repak/src/data.rs
@@ -153,7 +153,7 @@ where
         Some(compression) => {
             // https://github.com/EpicGames/UnrealEngine/commit/3aad0ff7976be1073005dca2c1282af548b45d89
             // Block size must fit into flags field or it may cause unreadable paks for earlier Unreal Engine versions
-            compression_block_size = 0x10000;
+            compression_block_size = 0x3e << 11; // max possible block size
             let mut compressed_size = 0;
             let mut blocks = vec![];
             for chunk in data.as_ref().chunks(compression_block_size as usize) {
diff --git a/repak/src/entry.rs b/repak/src/entry.rs
index a5fd649..73b514e 100644
--- a/repak/src/entry.rs
+++ b/repak/src/entry.rs
@@ -282,6 +282,11 @@ impl Entry {
         let is_uncompressed_size_32_bit_safe = self.uncompressed <= u32::MAX as u64;
         let is_offset_32_bit_safe = self.offset <= u32::MAX as u64;
 
+        assert!(
+            compression_blocks_count < 0x10_000,
+            "compression blocks count fits in 16 bits"
+        );
+
         let flags = (compression_block_size)
             | (compression_blocks_count << 6)
             | ((self.is_encrypted() as u32) << 22)