diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Revision history for rme
 
-## 0.1 -- TBA
+## 0.1.1
+
+* Added `Ord` instance for `RME`
+
+## 0.1
 
 * First version.
diff --git a/rme.cabal b/rme.cabal
--- a/rme.cabal
+++ b/rme.cabal
@@ -1,6 +1,6 @@
 Cabal-version:      3.0
 Name:               rme
-Version:            0.1
+Version:            0.1.1
 Author:             Galois, Inc.
 Maintainer:         huffman@galois.com
 Build-type:         Simple
diff --git a/src/Data/RME/Base.hs b/src/Data/RME/Base.hs
--- a/src/Data/RME/Base.hs
+++ b/src/Data/RME/Base.hs
@@ -29,7 +29,7 @@
 -- go deeper in the tree.
 
 data RME = Node !Int !RME !RME | R0 | R1
-  deriving (Eq, Show)
+  deriving (Eq, Ord, Show)
 
 -- | Evaluate formula with given variable assignment.
 eval :: RME -> (Int -> Bool) -> Bool