diff --git a/Scope/Types.hs b/Scope/Types.hs
index 8c253a5..242d232 100644
--- a/Scope/Types.hs
+++ b/Scope/Types.hs
@@ -49,9 +49,10 @@ module Scope.Types (
     , mkTransform
     , mkTSDataTransform
 
+    , translateRange
+    , unionRange
     , restrictRange
     , restrictRange01
-    , translateRange
     , zoomRange
 
     -- * Scope
@@ -138,6 +139,9 @@ instance Coordinate TimeStamp where
 translateRange :: Coordinate a => a -> (a, a) -> (a, a)
 translateRange t (x1, x2) = (translate t x1, translate t x2)
 
+unionRange :: Ord a => (a, a) -> (a, a) -> (a, a)
+unionRange (a1, a2) (b1, b2) = (min a1 b1, max a2 b2)
+
 -- | Restrict a window to within a given range
 restrictRange :: (Ord a, Coordinate a) => (a, a) -> (a, a) -> (a, a)
 restrictRange (rangeX1, rangeX2) (x1, x2)
diff --git a/src/GUI.hs b/src/GUI.hs
index 283a8bd..f9ef47f 100644
--- a/src/GUI.hs
+++ b/src/GUI.hs
@@ -578,7 +578,7 @@ layersFromFile path = do
         merge :: ([ScopeLayer], Maybe (TimeStamp, TimeStamp))
               -> ([ScopeLayer], Maybe (TimeStamp, TimeStamp))
               -> ([ScopeLayer], Maybe (TimeStamp, TimeStamp))
-        merge (ls1, bs1) (ls2, bs2) = (ls1 ++ ls2, mergeBounds bs1 bs2)
+        merge (ls1, bs1) (ls2, bs2) = (ls1 ++ ls2, unionBounds bs1 bs2)
 
         iterLayers (trackNo, color) = layers trackNo color <$>
             wholeTrackSummaryDouble standardIdentifiers trackNo
@@ -600,16 +600,16 @@ layersFromFile path = do
         yRange :: Summary Double -> Double
         yRange s = 2 * ((abs . numMin . summaryData $ s) + (abs . numMax . summaryData $ s))
 
-mergeBounds :: Ord a => Maybe (a, a) -> Maybe (a, a) -> Maybe (a, a)
-mergeBounds a               Nothing         = a
-mergeBounds Nothing         b               = b
-mergeBounds (Just (a1, a2)) (Just (b1, b2)) = Just (min a1 b1, max a2 b2)
+unionBounds :: Ord a => Maybe (a, a) -> Maybe (a, a) -> Maybe (a, a)
+unionBounds a         Nothing   = a
+unionBounds Nothing   b         = b
+unionBounds (Just r1) (Just r2) = Just (unionRange r1 r2)
 
 addLayersFromFile :: FilePath -> Scope -> IO Scope
 addLayersFromFile path scope = do
     (newLayers, newBounds) <- layersFromFile path
     let oldBounds = bounds scope
-        mb = mergeBounds oldBounds newBounds
+        mb = unionBounds oldBounds newBounds
         t = case oldBounds of
                 Just ob -> if oldBounds == mb
                                then id