diff --git a/Hledger/Interest.hs b/Hledger/Interest.hs
--- a/Hledger/Interest.hs
+++ b/Hledger/Interest.hs
@@ -13,6 +13,7 @@
 import Hledger.Interest.DayCountConvention
 import Hledger.Interest.Rate
 
+import Control.Monad
 import Control.Monad.RWS
 import Data.Decimal
 import Data.Maybe
diff --git a/hledger-interest.cabal b/hledger-interest.cabal
--- a/hledger-interest.cabal
+++ b/hledger-interest.cabal
@@ -1,5 +1,5 @@
 Name:                   hledger-interest
-Version:                1.6.5
+Version:                1.6.6
 Synopsis:               computes interest for a given account
 License:                BSD3
 License-file:           LICENSE
@@ -12,7 +12,7 @@
 Extra-source-files:     README.md
 Stability:              stable
 tested-with:            GHC == 8.4.4, GHC == 8.6.5, GHC == 8.8.4, GHC == 8.10.7,
-                        GHC == 9.0.2, GHC == 9.2.5, GHC == 9.4.4
+                        GHC == 9.0.2, GHC == 9.2.8, GHC == 9.4.7, GHC == 9.6.1
 
 Description:
  hledger-interest is a small command-line utility based on Simon
@@ -119,7 +119,7 @@
 Executable hledger-interest
   default-language:     Haskell2010
   Main-is:              Main.hs
-  Build-depends:        base >= 3 && < 5, hledger-lib >= 1.26 && < 1.29, time, mtl, Cabal, Decimal, text
+  Build-depends:        base >= 3 && < 5, hledger-lib >= 1.26 && < 1.31, time, mtl, Cabal, Decimal, text
   other-modules:        Hledger.Interest
                         Hledger.Interest.DayCountConvention
                         Hledger.Interest.Rate