diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,9 @@
+0.3.1.2 (18 Jan, 2019)
+======================
+
+- Allow `base-4.12` and `containers-0.6`
+- Fix build on GHC 8.6
+
 0.3.1.1 (21 May, 2016)
 ======================
 
diff --git a/MathObj/Monomial.hs b/MathObj/Monomial.hs
--- a/MathObj/Monomial.hs
+++ b/MathObj/Monomial.hs
@@ -71,7 +71,7 @@
 
 -- | The degree of a monomial is the sum of its exponents.
 degree :: T a -> Integer
-degree (Cons _ m) = M.fold (+) 0 m
+degree (Cons _ m) = M.foldr (+) 0 m
 
 -- | The \"partition degree\" of a monomial is the sum of the products
 --   of each variable index with its exponent.  For example, x1^3 x2^2
diff --git a/np-extras.cabal b/np-extras.cabal
--- a/np-extras.cabal
+++ b/np-extras.cabal
@@ -1,12 +1,12 @@
 name:           np-extras
-version:        0.3.1.1
+version:        0.3.1.2
 license:        BSD3
 license-file:   LICENSE
 build-type:     Simple
 cabal-version:  >= 1.10
-tested-with:    GHC == 7.4.2, GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.1, GHC == 8.0.1
+tested-with:    GHC == 7.4.2, GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.1, GHC == 8.0.1, GHC == 8.2.1, GHC == 8.4.1, GHC == 8.6.1
 author:         Brent Yorgey
-maintainer:     Brent Yorgey <byorgey@cis.upenn.edu>
+maintainer:     Brent Yorgey <byorgey@gmail.com>
 bug-reports:    http://hub.darcs.net/byorgey/np-extras/issues
 category:       Math
 synopsis:       NumericPrelude extras
@@ -18,10 +18,10 @@
   location: http://hub.darcs.net/byorgey/np-extras
 
 Library
-  build-depends: base >= 3.0 && < 4.10,
+  build-depends: base >= 3.0 && < 4.13,
                  numeric-prelude >= 0.3 && < 0.5,
                  primes >= 0.1.1 && < 0.3,
-                 containers >= 0.3 && < 0.6
+                 containers >= 0.3 && < 0.7
   exposed-modules:
     MathObj.FactoredRational
     MathObj.Monomial