diff --git a/CHANGES b/CHANGES
index 99a22a5d80..78d25d4246 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,8 @@
 
+2.5-591 | 2018-05-22 09:19:59 -0500
+
+  * Make Reassembler::TotalSize a constant time operation (Corelight)
+
 2.5-589 | 2018-05-21 21:37:54 +0000
 
   * Switch Bro's communication over to Broker; deprecate the old
diff --git a/VERSION b/VERSION
index 0b2f58b34d..dd91cbab0f 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.5-589
+2.5-591
diff --git a/src/Reassem.cc b/src/Reassem.cc
index a52bff01c6..0cdeadf80d 100644
--- a/src/Reassem.cc
+++ b/src/Reassem.cc
@@ -255,12 +255,7 @@ void Reassembler::ClearOldBlocks()
 
 uint64 Reassembler::TotalSize() const
 	{
-	uint64 size = 0;
-
-	for ( DataBlock* b = blocks; b; b = b->next )
-		size += b->Size();
-
-	return size;
+	return size_of_all_blocks;
 	}
 
 void Reassembler::Describe(ODesc* d) const