diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,3 +1,7 @@
+## 1.2.10
+
+* Increase upper-bound of `vector` to < 0.12.
+
 ## 1.2.9
 
 * Same changes as 1.2.8, but the 1.2.8 release was formed incorrectly and didn't
diff --git a/engine-io.cabal b/engine-io.cabal
--- a/engine-io.cabal
+++ b/engine-io.cabal
@@ -1,5 +1,5 @@
 name: engine-io
-version: 1.2.9
+version: 1.2.10
 synopsis: A Haskell implementation of Engine.IO
 homepage: http://github.com/ocharles/engine.io
 license: BSD3
@@ -42,7 +42,7 @@
     text >=0.11 && <1.3,
     transformers >=0.2 && <0.5,
     unordered-containers >=0.2 && <0.3,
-    vector >=0.10 && <0.11,
+    vector >=0.10 && <0.12,
     websockets >=0.8 && <0.10
 
   hs-source-dirs: src