diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,6 @@
+#####   3.2
+  fix bug in defaultReplacer  
+
 #####   3.1
   tidy up types: 
     
diff --git a/regex-do.cabal b/regex-do.cabal
--- a/regex-do.cabal
+++ b/regex-do.cabal
@@ -1,5 +1,5 @@
 name:                regex-do
-version:             3.1
+version:             3.2
 synopsis:            PCRE wrapper
 description:         format, search, replace (String | ByteString) with PCRE regex. Utf8-safe
 author:              Imants Cekusins
@@ -43,15 +43,14 @@
           
   ghc-options:  -fwarn-unused-imports
     
-  build-depends:  base <= 5.0,
-              regex-base,
-              regex-pcre,
-              stringsearch,
-              bytestring,
-              tagged,
-              array,
-              text
-
+  build-depends:  base > 4.7 && <= 5.0,
+                  array               >= 0.5.0,
+                  bytestring          >= 0.10.0,
+                  regex-base          >= 0.93.0,
+                  regex-pcre          >= 0.94.0,
+                  stringsearch        >= 0.3.0,
+                  tagged              >= 0.8.0,
+                  text                >= 1.2.0
 
   hs-source-dirs:      src
   default-language:    Haskell2010
diff --git a/src/Text/Regex/Do/Replace/Open.hs b/src/Text/Regex/Do/Replace/Open.hs
--- a/src/Text/Regex/Do/Replace/Open.hs
+++ b/src/Text/Regex/Do/Replace/Open.hs
@@ -31,8 +31,8 @@
     (Replace(..),
     defaultReplacer,
     getGroup,
-    replaceMatch
-    )
+    replaceMatch,
+    boundsOk)
     where
 
 import Text.Regex.Base.RegexLike as R
@@ -44,8 +44,6 @@
 import Text.Regex.Do.Type.Extract
 
 
-
-
 class Replace f repl body where
    replace::(Extract' body, ToArray arr) =>
         f arr -> repl -> body -> body
@@ -100,17 +98,27 @@
     another custom dynamic replacer could e.g.
     inspect all group matches before looking up a replacement.     -}
 defaultReplacer::Extract' a =>
-        Int         -- ^ group idx. 1-based
+        Int         -- ^ group idx. 0: full match, groups: 1.. see 'MatchArray'
         -> (a -> a) -- ^ (group match -> replacement) lookup
             -> GroupReplacer a
 defaultReplacer idx0 tweak0 = GroupReplacer fn1
-    where fn1 (ma0::MatchArray) acc0 = maybe acc0 fn1 mval1
-                where pl1 = ma0 A.! idx0 :: (R.MatchOffset, R.MatchLength)
-                      mval1 = getGroup acc0 ma0 idx0
-                      fn1 str1 = replaceMatch pl1 (str2, acc0)
-                                 where str2 = tweak0 str1
+    where fn1 (ma0::MatchArray) acc0 =
+            if boundsOk ma0 idx0 then maybe acc0 fn1 mval1
+            else acc0
+            where pl1 = ma0 A.! idx0 :: (R.MatchOffset, R.MatchLength)
+                  mval1 = getGroup acc0 ma0 idx0 
+                  fn1 str1 = replaceMatch pl1 (str2, acc0) 
+                             where str2 = tweak0 str1
 
 
+{- | check if specified group index is within 'MatchArray' bounds
+
+for use within 'GroupReplacer'
+-}
+boundsOk::MatchArray -> Int -> Bool
+boundsOk ma0 = inRange (bounds ma0)                         
+
+
 {- | get group content safely:
 
     * non-existing group idx will not error but return 'Nothing'
@@ -120,7 +128,7 @@
     -}
 getGroup::R.Extract a =>
     ReplaceAcc a -> MatchArray -> Int -> Maybe a
-getGroup acc0 ma0 idx0 = if idx0 < 1 || idx0 > P.length ma0 then Nothing     --  safety catch
+getGroup acc0 ma0 idx0 = if not (boundsOk ma0 idx0) then Nothing     --  safety catch
     else Just val1
     where pl1 = ma0 A.! idx0 :: (R.MatchOffset, R.MatchLength)
           pl2 = adjustPoslen pl1 acc0
diff --git a/test/TestRegex/TestReplaceOpen.hs b/test/TestRegex/TestReplaceOpen.hs
--- a/test/TestRegex/TestReplaceOpen.hs
+++ b/test/TestRegex/TestReplaceOpen.hs
@@ -18,10 +18,15 @@
             O.replace (Just [(4,3)::PosLen]) replacer ("abc 123 def"::Text) `shouldBe` ("abc [1-2-3] def"::Text)
           it "case 3" $
             O.replace ([[(4,3)::PosLen]]) replacer ("abc 123 def"::Text) `shouldBe` ("abc [1-2-3] def"::Text)
+          it "case 4" $
+            O.replace ([[]::[PosLen]]) replacer ("abc 123 def"::Text) `shouldBe` ("abc 123 def"::Text)
+          it "case 5" $
+            O.replace ([[(4,3)],[(8,3)],[(16,3)]]::[[PosLen]]) replacer ("abc 456 456 def 456"::Text) `shouldBe` ("abc 4 4 def 4"::Text)
 
 
 replacer::GroupReplacer Text
 replacer = defaultReplacer 1 tweak1
           where tweak1 str1 = case str1 of
                                 "123" -> "[1-2-3]"
+                                "456" -> "4"
                                 otherwise -> traceShow str1 "?"