diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,10 @@
 # Monoidal containers
 
+# 0.5.0.1
+
+  * Add a flag, `split-these`, to select whether to use the new "these"/"semialign" packages or the older combined "these" package.
+  * Add default.nix to make it easier to hack on this package in nix
+
 # 0.5.0.0
 
   * Added Data.IntMap.Monoidal and Data.IntMap.Monoidal.Strict, corresponding to Data.IntMap and Data.IntMap.Strict
diff --git a/monoidal-containers.cabal b/monoidal-containers.cabal
--- a/monoidal-containers.cabal
+++ b/monoidal-containers.cabal
@@ -1,5 +1,5 @@
 name:                monoidal-containers
-version:             0.5.0.0
+version:             0.5.0.1
 synopsis:            Containers with monoidal accumulation
 description:
     Containers with merging via monoidal accumulation. The 'Monoid' instances
@@ -30,6 +30,11 @@
   type:                git
   location:            git://github.com/bgamari/monoidal-containers
 
+flag split-these
+  description: Use split these/semialign packages
+  manual:      False
+  default:     True
+
 library
   exposed-modules:     Data.Map.Monoidal
                        Data.HashMap.Monoidal
@@ -46,10 +51,17 @@
                        containers >=0.5 && <0.7,
                        deepseq >=1.3 && <1.5,
                        unordered-containers >= 0.2 && < 0.3,
-                       hashable >= 1.2 && < 1.3,
+                       hashable >= 1.2 && < 1.4,
                        lens >=4.4 && <5,
                        newtype >=0.2 && <0.3,
-                       semigroups >= 0.18 && < 0.19,
-                       these <= 0.8.1
+                       semigroups >= 0.18 && < 0.20
+
+  if flag(split-these)
+    build-depends:     these >= 1 && <1.1,
+                       semialign >=1 && <1.1
+                    
+  else
+    build-depends:     these >= 0.7 && <0.9
+
   hs-source-dirs:      src
   default-language:    Haskell2010