diff --git a/reflex-dom-core/src/Reflex/Dom/Xhr.hs b/reflex-dom-core/src/Reflex/Dom/Xhr.hs
index 8bdf1e19..a06adad3 100644
--- a/reflex-dom-core/src/Reflex/Dom/Xhr.hs
+++ b/reflex-dom-core/src/Reflex/Dom/Xhr.hs
@@ -153,6 +153,7 @@ import Control.Lens
 import Control.Monad hiding (forM)
 import Control.Monad.IO.Class
 import Data.Aeson
+import Data.IORef (newIORef, atomicModifyIORef')
 #if MIN_VERSION_aeson(1,0,0)
 import Data.Aeson.Text
 #else
@@ -262,28 +263,34 @@ newXMLHttpRequestWithError req cb = do
     iforM_ (_xhrRequestConfig_headers c) $ xmlHttpRequestSetRequestHeader xhr
     maybe (return ()) (xmlHttpRequestSetResponseType xhr . fromResponseType) rt
     xmlHttpRequestSetWithCredentials xhr creds
+    -- Avoid handler being called more than once.
+    -- This is needed until jsaddle/ghcjs-dom: https://github.com/ghcjs/ghcjs-dom/issues/89 is fixed.
+    alreadyHandled <- liftIO $ newIORef False
     _ <- xmlHttpRequestOnreadystatechange xhr $ do
       readyState <- xmlHttpRequestGetReadyState xhr
       status <- xmlHttpRequestGetStatus xhr
       statusText <- xmlHttpRequestGetStatusText xhr
-      when (readyState == 4) $ do
-        t <- if rt == Just XhrResponseType_Text || isNothing rt
-             then xmlHttpRequestGetResponseText xhr
-             else return Nothing
-        r <- xmlHttpRequestGetResponse xhr
-        h <- case _xhrRequestConfig_responseHeaders c of
-          AllHeaders -> parseAllHeadersString <$>
-            xmlHttpRequestGetAllResponseHeaders xhr
-          OnlyHeaders xs -> traverse (xmlHttpRequestGetResponseHeader xhr)
-            (Map.fromSet id xs)
-        _ <- liftJSM $ cb $ Right
-             XhrResponse { _xhrResponse_status = status
-                         , _xhrResponse_statusText = statusText
-                         , _xhrResponse_response = r
-                         , _xhrResponse_responseText = t
-                         , _xhrResponse_headers = h
-                         }
-        return ()
+      when (readyState == 4) $
+        handled <- liftIO $ atomicModifyIORef' alreadyHandled $
+          \handled -> (True, handled)
+        unless handled $ do
+          t <- if rt == Just XhrResponseType_Text || isNothing rt
+               then xmlHttpRequestGetResponseText xhr
+               else return Nothing
+          r <- xmlHttpRequestGetResponse xhr
+          h <- case _xhrRequestConfig_responseHeaders c of
+            AllHeaders -> parseAllHeadersString <$>
+              xmlHttpRequestGetAllResponseHeaders xhr
+            OnlyHeaders xs -> traverse (xmlHttpRequestGetResponseHeader xhr)
+              (Map.fromSet id xs)
+          _ <- liftJSM $ cb $ Right
+               XhrResponse { _xhrResponse_status = status
+                           , _xhrResponse_statusText = statusText
+                           , _xhrResponse_response = r
+                           , _xhrResponse_responseText = t
+                           , _xhrResponse_headers = h
+                           }
+          return ()
     _ <- xmlHttpRequestSend xhr (_xhrRequestConfig_sendData c)
     return ()
   return xhr