diff --git a/src/ShellCheck/Fixer.hs b/src/ShellCheck/Fixer.hs
index a393cec..75b6fdd 100644
--- a/src/ShellCheck/Fixer.hs
+++ b/src/ShellCheck/Fixer.hs
@@ -1,9 +1,44 @@
-module ShellCheck.Fixer (applyFix , replaceMultiLines) where
+module ShellCheck.Fixer (applyFix , replaceMultiLines, Ranged(..)) where
 
 import ShellCheck.Interface
-
 import Data.List
 
+-- The Ranged class is used for types that has a start and end position.
+class Ranged a where
+    start   :: a -> Position
+    end     :: a -> Position
+    overlap :: a -> a -> Bool
+    overlap x y =
+        (yStart >= xStart && yStart < xEnd) || (yStart < xStart && yEnd > xStart)
+        where
+            yStart = start y
+            yEnd = end y
+            xStart = start x
+            xEnd = end x
+
+instance Ranged Replacement where
+    start = repStartPos
+    end   = repEndPos
+
+instance Ranged a => Ranged [a] where
+    start [] = newPosition
+    start xs = (minimum . map start) xs
+    end []   = newPosition
+    end xs   = (maximum . map end) xs
+
+instance Ranged Fix where
+    start = start . fixReplacements
+    end   = end . fixReplacements
+
+-- The Monoid instance for Fix merges replacements that do not overlap.
+instance Monoid Fix where
+    mempty = newFix
+
+instance Semigroup Fix where
+    f1 <> f2 = if overlap f1 f2 then f1 else newFix {
+            fixReplacements = fixReplacements f1 ++ fixReplacements f2
+    }
+
 applyFix fix fileLines =
     -- apply replacements in sorted order by end position
     let sorted = (removeOverlap . reverse . sort) (fixReplacements fix) in
diff --git a/src/ShellCheck/Interface.hs b/src/ShellCheck/Interface.hs
index c0bf79f..ea70c15 100644
--- a/src/ShellCheck/Interface.hs
+++ b/src/ShellCheck/Interface.hs
@@ -54,7 +54,6 @@ module ShellCheck.Interface
     , newFix
     , Replacement(repStartPos, repEndPos, repString)
     , newReplacement
-    , Ranged(overlap)
     ) where
 
 import ShellCheck.AST
@@ -274,36 +273,3 @@ mockedSystemInterface files = SystemInterface {
             [] -> return $ Left "File not included in mock."
             [(_, contents)] -> return $ Right contents
 
--- The Ranged class is used for types that has a start and end position.
-class Ranged a where
-    start   :: a -> Position
-    end     :: a -> Position
-    overlap :: a -> a -> Bool
-    overlap x y =
-        (yStart >= xStart && yStart < xEnd) || (yStart < xStart && yEnd > xStart)
-        where
-            yStart = start y
-            yEnd = end y
-            xStart = start x
-            xEnd = end x
-
-instance Ranged Replacement where
-    start = repStartPos
-    end   = repEndPos
-
-instance Ranged a => Ranged [a] where
-    start [] = newPosition
-    start xs = (minimum . map start) xs
-    end []   = newPosition
-    end xs   = (maximum . map end) xs
-
-instance Ranged Fix where
-    start = start . fixReplacements
-    end   = end . fixReplacements
-
--- The Monoid instance for Fix merges replacements that do not overlap.
-instance Monoid Fix where
-    mempty = newFix
-    f1 `mappend` f2 = if overlap f1 f2 then f1 else newFix {
-            fixReplacements = fixReplacements f1 ++ fixReplacements f2
-        }