diff --git a/src-3.0/GF/System/NoReadline.hs b/src-3.0/GF/System/NoReadline.hs
index 138ba4e28..564200a3e 100644
--- a/src-3.0/GF/System/NoReadline.hs
+++ b/src-3.0/GF/System/NoReadline.hs
@@ -12,7 +12,7 @@
 -- Do not use readline.
 -----------------------------------------------------------------------------
 
-module GF.System.NoReadline (fetchCommand) where
+module GF.System.NoReadline (fetchCommand, setCompletionFunction) where
 
 import System.IO.Error (try)
 import System.IO (stdout,hFlush)
@@ -25,3 +25,6 @@ fetchCommand s = do
   case res of
    Left e -> return "q"
    Right l -> return l
+
+setCompletionFunction :: Maybe (String -> String -> Int -> IO [String]) -> IO ()
+setCompletionFunction _ = return ()
diff --git a/src-3.0/GF/System/Readline.hs b/src-3.0/GF/System/Readline.hs
index c12493f98..94fca89bd 100644
--- a/src-3.0/GF/System/Readline.hs
+++ b/src-3.0/GF/System/Readline.hs
@@ -14,14 +14,14 @@
 -- Uses the right readline library to read user input.
 -----------------------------------------------------------------------------
 
-module GF.System.Readline (fetchCommand) where
+module GF.System.Readline (fetchCommand, setCompletionFunction) where
 
 #ifdef USE_READLINE
 
-import GF.System.UseReadline (fetchCommand)
+import GF.System.UseReadline (fetchCommand, setCompletionFunction)
 
 #else
 
-import GF.System.NoReadline (fetchCommand)
+import GF.System.NoReadline (fetchCommand, setCompletionFunction)
 
 #endif
diff --git a/src-3.0/GF/System/UseReadline.hs b/src-3.0/GF/System/UseReadline.hs
index c84b9d7f4..c4a8f9239 100644
--- a/src-3.0/GF/System/UseReadline.hs
+++ b/src-3.0/GF/System/UseReadline.hs
@@ -12,9 +12,9 @@
 -- Use GNU readline
 -----------------------------------------------------------------------------
 
-module GF.System.UseReadline (fetchCommand) where
+module GF.System.UseReadline (fetchCommand, setCompletionFunction) where
 
-import System.Console.Readline (readline, addHistory)
+import System.Console.Readline
 
 fetchCommand :: String -> IO (String)
 fetchCommand s = do
@@ -23,3 +23,12 @@ fetchCommand s = do
    Nothing -> return "q"
    Just s -> do addHistory s
                 return s
+
+setCompletionFunction :: Maybe (String -> String -> Int -> IO [String]) -> IO ()
+setCompletionFunction Nothing   = setCompletionEntryFunction Nothing
+setCompletionFunction (Just fn) = setCompletionEntryFunction (Just my_fn)
+  where
+    my_fn prefix = do
+      s <- getLineBuffer
+      p <- getPoint
+      fn s prefix p