diff --git a/ShellCheck/AST.hs b/ShellCheck/AST.hs
index e664917..69bd046 100644
--- a/ShellCheck/AST.hs
+++ b/ShellCheck/AST.hs
@@ -25,6 +25,7 @@ data Id = Id Int deriving (Show, Eq, Ord)
 
 data Quoted = Quoted | Unquoted deriving (Show, Eq)
 data Dashed = Dashed | Undashed deriving (Show, Eq)
+data AssignmentMode = Assign | Append deriving (Show, Eq)
 
 data Token =
     TA_Base Id String Token
@@ -45,7 +46,7 @@ data Token =
     | T_AndIf Id (Token) (Token)
     | T_Arithmetic Id Token
     | T_Array Id [Token]
-    | T_Assignment Id String Token
+    | T_Assignment Id AssignmentMode String (Maybe Token) Token
     | T_Backgrounded Id Token
     | T_Backticked Id [Token]
     | T_Bang Id
@@ -137,6 +138,11 @@ analyze f g i t =
         return . i $ newT
     roundAll = mapM round
 
+    roundMaybe Nothing = return Nothing
+    roundMaybe (Just v) = do
+        s <- round v
+        return (Just s)
+
     dl l v = do
         x <- roundAll l
         return $ v x
@@ -162,7 +168,10 @@ analyze f g i t =
     delve (T_IoFile id op file) = d2 op file $ T_IoFile id
     delve (T_HereString id word) = d1 word $ T_HereString id
     delve (T_FdRedirect id v t) = d1 t $ T_FdRedirect id v
-    delve (T_Assignment id v t) = d1 t $ T_Assignment id v
+    delve (T_Assignment id mode var index value) = do
+        a <- roundMaybe index
+        b <- round value
+        return $ T_Assignment id mode var a b
     delve (T_Array id t) = dl t $ T_Array id
     delve (T_Redirecting id redirs cmd) = do
         a <- roundAll redirs
@@ -279,7 +288,7 @@ getId t = case t of
         T_HereDoc id _ _ _ _ -> id
         T_HereString id _  -> id
         T_FdRedirect id _ _  -> id
-        T_Assignment id _ _  -> id
+        T_Assignment id _ _ _ _  -> id
         T_Array id _  -> id
         T_Redirecting id _ _  -> id
         T_SimpleCommand id _ _  -> id
diff --git a/ShellCheck/Analytics.hs b/ShellCheck/Analytics.hs
index 20e6b07..6af4841 100644
--- a/ShellCheck/Analytics.hs
+++ b/ShellCheck/Analytics.hs
@@ -285,7 +285,7 @@ prop_checkAssignAteCommand2 = verify checkAssignAteCommand "A=ls --sort=$foo"
 prop_checkAssignAteCommand3 = verify checkAssignAteCommand "A=cat foo | grep bar"
 prop_checkAssignAteCommand4 = verifyNot checkAssignAteCommand "A=foo ls -l"
 prop_checkAssignAteCommand5 = verifyNot checkAssignAteCommand "PAGER=cat grep bar"
-checkAssignAteCommand (T_SimpleCommand id ((T_Assignment _ _ assignmentTerm):[]) (firstWord:_)) =
+checkAssignAteCommand (T_SimpleCommand id ((T_Assignment _ _ _ _ assignmentTerm):[]) (firstWord:_)) =
     when ("-" `isPrefixOf` (concat $ deadSimple firstWord) ||
         (isCommonCommand (getLiteralString assignmentTerm) && not (isCommonCommand (getLiteralString firstWord)))) $
             warn id "To assign the output of a command, use var=$(cmd) ."
@@ -880,7 +880,7 @@ inUnquotableContext tree t =
         TA_Binary _ _ _ _ -> True
         TA_Trinary _ _ _ _ -> True
         TA_Expansion _ _ -> True
-        T_Assignment _ _ _ -> True
+        T_Assignment _ _ _ _ _ -> True
         T_Redirecting _ _ _ ->
             any (isCommand t) ["local", "declare", "typeset", "export"]
         T_DoubleQuoted _ _ -> True
@@ -1138,7 +1138,7 @@ prop_checkPS15 = verifyNot checkPS1Assignments "PS1='\\[\\033[1;35m\\]\\$ '"
 prop_checkPS16 = verifyNot checkPS1Assignments "PS1='\\[\\e1m\\e[1m\\]\\$ '"
 prop_checkPS17 = verifyNot checkPS1Assignments "PS1='e033x1B'"
 prop_checkPS18 = verifyNot checkPS1Assignments "PS1='\\[\\e\\]'"
-checkPS1Assignments (T_Assignment _ "PS1" word) = warnFor word
+checkPS1Assignments (T_Assignment _ _ "PS1" _ word) = warnFor word
   where
     warnFor word =
         let contents = concat $ deadSimple word in
@@ -1386,7 +1386,7 @@ getModifiedVariables t =
     case t of
         T_SimpleCommand _ vars [] ->
             concatMap (\x -> case x of
-                                T_Assignment id name w ->
+                                T_Assignment id _ name _ w ->
                                     [(x, x, name, DataFrom [w])]
                                 _ -> []
                       ) vars
@@ -1411,7 +1411,7 @@ getReferencedVariableCommand base@(T_SimpleCommand _ _ ((T_NormalWord _ ((T_Lite
         "export" -> concatMap getReference rest
         _ -> [(base,base, x)]
   where
-    getReference t@(T_Assignment _ name value) = [(t, t, name)]
+    getReference t@(T_Assignment _ _ name _ value) = [(t, t, name)]
     getReference t@(T_NormalWord _ [T_Literal _ name]) | not ("-" `isPrefixOf` name) = [(t, t, name)]
     getReference _ = []
 
@@ -1446,7 +1446,7 @@ getModifiedVariableCommand base@(T_SimpleCommand _ _ ((T_NormalWord _ ((T_Litera
         [(base, t, s, DataExternal)]
     getLiteral x = []
 
-    getModifierParam t@(T_Assignment _ name value) =
+    getModifierParam t@(T_Assignment _ _ name _ value) =
         [(base, t, name, DataFrom [value])]
     getModifierParam _ = []
 
@@ -1464,6 +1464,7 @@ getReferencedVariables t =
     case t of
         T_DollarBraced id l -> map (\x -> (t, t, x)) $ [getBracedReference $ bracedString l]
         TA_Variable id str -> [(t, t, str)]
+        T_Assignment id Append str _ _ -> [(t, t, str)]
         x -> getReferencedVariableCommand x
 
 getVariableFlow t =
@@ -1692,6 +1693,7 @@ prop_checkUnused7 = verifyNotFull checkUnusedAssignments "var=2; $((var))"
 prop_checkUnused8 = verifyFull checkUnusedAssignments "var=2; var=3;"
 prop_checkUnused9 = verifyNotFull checkUnusedAssignments "read ''"
 prop_checkUnused10= verifyNotFull checkUnusedAssignments "read -p 'test: '"
+prop_checkUnused11= verifyNotFull checkUnusedAssignments "bar=5; export foo[$bar]=3"
 checkUnusedAssignments t = snd $ runState (mapM_ checkAssignment flow) []
   where
     flow = getVariableFlow t
diff --git a/ShellCheck/Parser.hs b/ShellCheck/Parser.hs
index 03ebb29..0212dc1 100644
--- a/ShellCheck/Parser.hs
+++ b/ShellCheck/Parser.hs
@@ -1143,7 +1143,7 @@ makeSimpleCommand id1 id2 prefix cmd suffix =
     in
         T_Redirecting id1 redirs $ T_SimpleCommand id2 assigns args
   where
-    assignment (T_Assignment _ _ _) = True
+    assignment (T_Assignment _ _ _ _ _) = True
     assignment _ = False
     redirection (T_FdRedirect _ _ _) = True
     redirection _ = False
@@ -1538,35 +1538,40 @@ readAssignmentWord = try $ do
     variable <- readVariableName
     optional (readNormalDollar >> parseNoteAt pos ErrorC
                                 "For indirection, use (associative) arrays or 'read \"var$n\" <<< \"value\"'")
-    optional readArrayIndex -- Throws away the index. Fixme?
+    index <- optionMaybe readArrayIndex
     space <- spacing
     pos <- getPosition
-    op <- string "+=" <|> string "="  -- analysis doesn't treat += as a reference. fixme?
+    op <- readAssignmentOp
     space2 <- spacing
     if space == "" && space2 /= ""
       then do
         when (variable /= "IFS") $
             parseNoteAt pos InfoC $ "Note that 'var= value' (with space after equals sign) is similar to 'var=\"\"; value'."
         value <- readEmptyLiteral
-        return $ T_Assignment id variable value
+        return $ T_Assignment id op variable index value
       else do
         when (space /= "" || space2 /= "") $
             parseNoteAt pos ErrorC "Don't put spaces around the = in assignments."
         value <- readArray <|> readNormalWord
         spacing
-        return $ T_Assignment id variable value
+        return $ T_Assignment id op variable index value
   where
+    readAssignmentOp =
+        (string "+=" >> return Append) <|> (string "=" >> return Assign)
     readEmptyLiteral = do
         id <- getNextId
         return $ T_Literal id ""
 
 -- This is only approximate. Fixme?
+-- * Bash allows foo[' ' "" $(true) 2 ``]=var
+-- * foo[bar] dereferences bar
 readArrayIndex = do
     char '['
     optional space
     x <- readNormalishWord "]"
     optional space
     char ']'
+    return x
 
 readArray = called "array assignment" $ do
     id <- getNextId