diff --git a/hledger-lib/Hledger/Utils/Regex.hs b/hledger-lib/Hledger/Utils/Regex.hs
index c944ae26f..3b377e28d 100644
--- a/hledger-lib/Hledger/Utils/Regex.hs
+++ b/hledger-lib/Hledger/Utils/Regex.hs
@@ -17,7 +17,12 @@ Easy regular expression helpers, currently based on regex-tdfa. These should:
 
 - have simple monomorphic types
 
-- work with strings
+- work with simple strings
+
+Regex strings are automatically compiled into regular expressions the
+first time they are seen, and these are cached. If you use a huge
+number of unique regular expressions this might lead to increased
+memory usage.
 
 Current limitations:
 
@@ -42,6 +47,7 @@ where
 import Data.Array
 import Data.Char
 import Data.List (foldl')
+import Data.MemoUgly (memo)
 import Text.Regex.TDFA (
   Regex, CompOption(..), ExecOption(..), defaultCompOpt, defaultExecOpt,
   makeRegexOpts, AllMatches(getAllMatches), match, (=~), MatchText
@@ -60,10 +66,10 @@ type Replacement = String
 -- | Convert our string-based regexps to real ones. Can fail if the
 -- string regexp is malformed.
 toRegex :: Regexp -> Regex
-toRegex = makeRegexOpts compOpt execOpt
+toRegex = memo (makeRegexOpts compOpt execOpt)
 
 toRegexCI :: Regexp -> Regex
-toRegexCI = makeRegexOpts compOpt{caseSensitive=False} execOpt
+toRegexCI = memo (makeRegexOpts compOpt{caseSensitive=False} execOpt)
 
 compOpt :: CompOption
 compOpt = defaultCompOpt
diff --git a/hledger-lib/hledger-lib.cabal b/hledger-lib/hledger-lib.cabal
index 642d130f0..28fc625de 100644
--- a/hledger-lib/hledger-lib.cabal
+++ b/hledger-lib/hledger-lib.cabal
@@ -68,6 +68,7 @@ library
     , safe >= 0.2
     , split >= 0.1 && < 0.3
     , transformers >= 0.2 && < 0.5
+    , uglymemo
     , utf8-string >= 0.3.5 && < 1.1
     , HUnit
 
@@ -145,6 +146,7 @@ test-suite tests
     , safe >= 0.2
     , split >= 0.1 && < 0.3
     , transformers >= 0.2 && < 0.5
+    , uglymemo
     , utf8-string >= 0.3.5 && < 1.1
     , HUnit
     , hledger-lib
diff --git a/hledger-lib/package.yaml b/hledger-lib/package.yaml
index edabcd668..f6d51a896 100644
--- a/hledger-lib/package.yaml
+++ b/hledger-lib/package.yaml
@@ -66,6 +66,7 @@ dependencies:
   - safe >= 0.2
   - split >= 0.1 && < 0.3
   - transformers >= 0.2 && < 0.5
+  - uglymemo
   - utf8-string >= 0.3.5 && < 1.1
   - HUnit
 # XXX not supported
diff --git a/stack.yaml b/stack.yaml
index a9d14f2e5..eb4b7e20b 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -13,4 +13,9 @@ flags:
 extra-deps:
 - brick-0.2
 - text-zipper-0.2.1
+- uglymemo-0.1.0.1
 - vty-5.3.1
+
+ghc-options:
+  rtsopts:
+    all