diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,8 @@
+5.9.1
+  - Vty now only emits UTF8 charset sequences in terminals without a
+    preexisting UTF8 declaration to avoid emitting garbage sequences
+    (fixes #89)
+
 5.9
   - Added new Output methods supportsBell and ringTerminalBell to find out
     whether the output device has an audio bell and to ring it (see #102)
diff --git a/src/Graphics/Vty/Output/XTermColor.hs b/src/Graphics/Vty/Output/XTermColor.hs
--- a/src/Graphics/Vty/Output/XTermColor.hs
+++ b/src/Graphics/Vty/Output/XTermColor.hs
@@ -21,12 +21,17 @@
 
 import System.Posix.IO (fdWrite)
 import System.Posix.Types (Fd)
+import System.Posix.Env (getEnv)
 
 #if !(MIN_VERSION_base(4,8,0))
 import Control.Applicative
 import Data.Foldable (foldMap)
 #endif
 
+import Data.List (isInfixOf)
+import Data.Maybe (catMaybes)
+import Data.Monoid ((<>))
+
 -- | Initialize the display to UTF-8. 
 reserveTerminal :: ( Applicative m, MonadIO m ) => String -> Fd -> m Output
 reserveTerminal variant outFd = liftIO $ do
@@ -34,7 +39,9 @@
     -- If the terminal variant is xterm-color use xterm instead since, more often than not,
     -- xterm-color is broken.
     let variant' = if variant == "xterm-color" then "xterm" else variant
-    flushedPut setUtf8CharSet
+
+    utf8a <- utf8Active
+    when (not utf8a) $ flushedPut setUtf8CharSet
     t <- TerminfoBased.reserveTerminal variant' outFd
 
     mouseModeStatus <- newIORef False
@@ -61,7 +68,7 @@
     let t' = t
              { terminalID = terminalID t ++ " (xterm-color)"
              , releaseTerminal = do
-                 liftIO $ flushedPut setDefaultCharSet
+                 when (not utf8a) $ liftIO $ flushedPut setDefaultCharSet
                  setMode t' BracketedPaste False
                  setMode t' Mouse False
                  releaseTerminal t
@@ -73,6 +80,14 @@
              , setMode = xtermSetMode t'
              }
     return t'
+
+utf8Active :: IO Bool
+utf8Active = do
+    let vars = ["LC_ALL", "LANG", "LC_CTYPE"]
+    results <- catMaybes <$> mapM getEnv vars
+    let matches = filter ("UTF8" `isInfixOf`) results <>
+                  filter ("UTF-8" `isInfixOf`) results
+    return $ not $ null matches
 
 -- | Enable bracketed paste mode:
 -- http://cirw.in/blog/bracketed-paste
diff --git a/vty.cabal b/vty.cabal
--- a/vty.cabal
+++ b/vty.cabal
@@ -1,5 +1,5 @@
 name:                vty
-version:             5.9
+version:             5.9.1
 license:             BSD3
 license-file:        LICENSE
 author:              AUTHORS