diff --git a/library/Text/Regex/PCRE/Heavy.hs b/library/Text/Regex/PCRE/Heavy.hs
--- a/library/Text/Regex/PCRE/Heavy.hs
+++ b/library/Text/Regex/PCRE/Heavy.hs
@@ -1,7 +1,10 @@
 {-# OPTIONS_GHC -fno-warn-orphans -fno-warn-unused-binds #-}
 {-# LANGUAGE NoImplicitPrelude, UndecidableInstances, FlexibleInstances, FlexibleContexts, BangPatterns #-}
 {-# LANGUAGE TemplateHaskell, QuasiQuotes, UnicodeSyntax #-}
-{-# LANGUAGE ForeignFunctionInterface #-}
+{-# LANGUAGE ForeignFunctionInterface, CPP #-}
+#if __GLASGOW_HASKELL__ < 710
+{-# LANGUAGE OverlappingInstances #-}
+#endif
 
 -- | A usable regular expressions library on top of pcre-light.
 module Text.Regex.PCRE.Heavy (
@@ -70,7 +73,7 @@
 (≈) = (=~)
 
 -- | Does raw PCRE matching (you probably shouldn't use this directly).
--- 
+--
 -- >>> :set -XOverloadedStrings
 -- >>> rawMatch [re|\w{2}|] "a a ab abc ba" 0 []
 -- Just [(4,6)]
@@ -202,6 +205,9 @@
 --
 -- >>> gsub [re|bad|] "xxxbad" "this is bad, right? bad" :: String
 -- "this is xxxbad, right? xxxbad"
+--
+-- >>> gsub [re|a|] "" "aaa" :: String
+-- ""
 gsub ∷ (ConvertibleStrings SBS a, ConvertibleStrings a SBS, RegexReplacement r) ⇒ Regex → r → a → a
 gsub r t s = gsubO r [] t s
 
@@ -209,11 +215,15 @@
 gsubO ∷ (ConvertibleStrings SBS a, ConvertibleStrings a SBS, RegexReplacement r) ⇒ Regex → [PCREExecOption] → r → a → a
 gsubO r opts t s = cs $ loop 0 str
   where str = toSBS s
-        loop offset acc =
-          case rawSub r t acc offset opts of
+        loop offset acc
+          | offset >= l = acc
+          | otherwise = case rawSub r t acc offset opts of
             Just (result, newOffset) →
-              if newOffset == offset then acc else loop newOffset result
+              if newOffset == offset && l == BS.length result
+              then acc
+              else loop newOffset result
             _ → acc
+          where l = BS.length acc
 
 -- | Splits the string using the given regex.
 --
diff --git a/pcre-heavy.cabal b/pcre-heavy.cabal
--- a/pcre-heavy.cabal
+++ b/pcre-heavy.cabal
@@ -1,5 +1,5 @@
 name:            pcre-heavy
-version:         1.0.0.1
+version:         1.0.0.2
 synopsis:        A regexp library on top of pcre-light you can actually use.
 description:
     A regular expressions library that does not suck.