diff --git a/src/bin/loop_server.rs b/src/bin/loop_server.rs
index df62043..0967182 100644
--- a/src/bin/loop_server.rs
+++ b/src/bin/loop_server.rs
@@ -92,7 +92,7 @@ fn create_loop() -> WebmServer {
                         // TODO: this is incorrect, condition needs to also affirm we're the first video block of the cluster
                         chunk.mark_keyframe(true);
                     }
-                    chunk.extend_timespan(cluster_timecode + (block.timecode as u64));
+                    chunk.observe_simpleblock_timecode(block.timecode);
                 }
                 encode_webm_element(&SimpleBlock(*block), &mut buffer).unwrap();
             },
diff --git a/src/chunk.rs b/src/chunk.rs
index 5a0dc2d..20b29cf 100644
--- a/src/chunk.rs
+++ b/src/chunk.rs
@@ -47,10 +47,11 @@ impl<B: AsRef<[u8]>> Chunk<B> {
             *bytes_used = cursor.position() as u8;
         }
     }
-    pub fn extend_timespan(&mut self, timecode: u64) {
+    pub fn observe_simpleblock_timecode(&mut self, timecode: i16) {
         if let &mut Chunk::ClusterHead {start, ref mut end, ..} = self {
-            if timecode > start {
-                *end = timecode;
+            let absolute_timecode = start + (timecode as u64);
+            if absolute_timecode > start {
+                *end = absolute_timecode;
             }
         }
     }