diff --git a/src/java/org/apache/cassandra/io/compress/CompressedSequentialWriter.java b/src/java/org/apache/cassandra/io/compress/CompressedSequentialWriter.java
index 7b72105bbc..6b3b853460 100644
--- a/src/java/org/apache/cassandra/io/compress/CompressedSequentialWriter.java
+++ b/src/java/org/apache/cassandra/io/compress/CompressedSequentialWriter.java
@@ -150,6 +150,8 @@ public class CompressedSequentialWriter extends SequentialWriter
     {
         if (overrideLength <= 0)
             return metadataWriter.open(originalSize, chunkOffset, isFinal ? FINAL : SHARED_FINAL);
+        // we are early opening the file, make sure we open metadata with the correct size
+        assert !isFinal;
         return metadataWriter.open(overrideLength, chunkOffset, SHARED);
     }
 
diff --git a/src/java/org/apache/cassandra/io/compress/CompressionMetadata.java b/src/java/org/apache/cassandra/io/compress/CompressionMetadata.java
index 55de306935..84fb39fde0 100644
--- a/src/java/org/apache/cassandra/io/compress/CompressionMetadata.java
+++ b/src/java/org/apache/cassandra/io/compress/CompressionMetadata.java
@@ -352,6 +352,7 @@ public class CompressionMetadata
                         this.offsets.unreference();
                     }
                     // null out our reference to the original shared data to catch accidental reuse
+                    // note that since noone is writing to this Writer while we open it, null:ing out this.offsets is safe
                     this.offsets = null;
                     if (type == OpenType.SHARED_FINAL)
                     {