diff --git a/ShellCheck.cabal b/ShellCheck.cabal
index 8956ff5..4a9e615 100644
--- a/ShellCheck.cabal
+++ b/ShellCheck.cabal
@@ -53,6 +53,7 @@ library
       base > 4.6.0.1 && < 5,
       bytestring,
       containers >= 0.5,
+      deepseq >= 1.4.0.0,
       directory,
       mtl >= 2.2.1,
       parsec,
@@ -89,6 +90,7 @@ executable shellcheck
       aeson,
       base >= 4 && < 5,
       bytestring,
+      deepseq >= 1.4.0.0,
       ShellCheck,
       containers,
       directory,
@@ -104,6 +106,7 @@ test-suite test-shellcheck
       aeson,
       base >= 4 && < 5,
       bytestring,
+      deepseq >= 1.4.0.0,
       ShellCheck,
       containers,
       directory,
diff --git a/src/ShellCheck/AST.hs b/src/ShellCheck/AST.hs
index cd96165..8a6d7b2 100644
--- a/src/ShellCheck/AST.hs
+++ b/src/ShellCheck/AST.hs
@@ -17,14 +17,17 @@
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 -}
+{-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}
 module ShellCheck.AST where
 
+import GHC.Generics (Generic)
 import Control.Monad.Identity
+import Control.DeepSeq
 import Text.Parsec
 import qualified ShellCheck.Regex as Re
 import Prelude hiding (id)
 
-newtype Id = Id Int deriving (Show, Eq, Ord)
+newtype Id = Id Int deriving (Show, Eq, Ord, Generic, NFData)
 
 data Quoted = Quoted | Unquoted deriving (Show, Eq)
 data Dashed = Dashed | Undashed deriving (Show, Eq)
diff --git a/src/ShellCheck/AnalyzerLib.hs b/src/ShellCheck/AnalyzerLib.hs
index 1639ff6..9b7892d 100644
--- a/src/ShellCheck/AnalyzerLib.hs
+++ b/src/ShellCheck/AnalyzerLib.hs
@@ -20,26 +20,28 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TemplateHaskell  #-}
 module ShellCheck.AnalyzerLib where
-import           ShellCheck.AST
-import           ShellCheck.ASTLib
-import           ShellCheck.Data
-import           ShellCheck.Interface
-import           ShellCheck.Parser
-import           ShellCheck.Regex
 
-import           Control.Arrow          (first)
-import           Control.Monad.Identity
-import           Control.Monad.RWS
-import           Control.Monad.State
-import           Control.Monad.Writer
-import           Data.Char
-import           Data.List
-import qualified Data.Map               as Map
-import           Data.Maybe
-import           Data.Semigroup
+import ShellCheck.AST
+import ShellCheck.ASTLib
+import ShellCheck.Data
+import ShellCheck.Interface
+import ShellCheck.Parser
+import ShellCheck.Regex
 
-import           Test.QuickCheck.All    (forAllProperties)
-import           Test.QuickCheck.Test   (maxSuccess, quickCheckWithResult, stdArgs)
+import Control.Arrow (first)
+import Control.DeepSeq
+import Control.Monad.Identity
+import Control.Monad.RWS
+import Control.Monad.State
+import Control.Monad.Writer
+import Data.Char
+import Data.List
+import Data.Maybe
+import Data.Semigroup
+import qualified Data.Map as Map
+
+import Test.QuickCheck.All (forAllProperties)
+import Test.QuickCheck.Test (maxSuccess, quickCheckWithResult, stdArgs)
 
 type Analysis = AnalyzerM ()
 type AnalyzerM a = RWS Parameters [TokenComment] Cache a
@@ -143,7 +145,7 @@ makeComment severity id code note =
         }
     }
 
-addComment note = tell [note]
+addComment note = note `deepseq` tell [note]
 
 warn :: MonadWriter [TokenComment] m => Id -> Code -> String -> m ()
 warn  id code str = addComment $ makeComment WarningC id code str
@@ -159,10 +161,11 @@ warnWithFix id code str fix = addComment $
 
 makeCommentWithFix :: Severity -> Id -> Code -> String -> Fix -> TokenComment
 makeCommentWithFix severity id code str fix =
-    let comment = makeComment severity id code str in
-    comment {
-        tcFix = Just fix
-    }
+    let comment = makeComment severity id code str
+        withFix = comment {
+            tcFix = Just fix
+        }
+    in withFix `deepseq` withFix
 
 makeParameters spec =
     let params = Parameters {
diff --git a/src/ShellCheck/Interface.hs b/src/ShellCheck/Interface.hs
index 4a7214b..092b9e8 100644
--- a/src/ShellCheck/Interface.hs
+++ b/src/ShellCheck/Interface.hs
@@ -17,6 +17,7 @@
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 -}
+{-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}
 module ShellCheck.Interface
     (
     SystemInterface(..)
@@ -56,8 +57,11 @@ module ShellCheck.Interface
     ) where
 
 import ShellCheck.AST
+
+import Control.DeepSeq
 import Control.Monad.Identity
 import Data.Monoid
+import GHC.Generics (Generic)
 import qualified Data.Map as Map
 
 
@@ -170,12 +174,13 @@ data ExecutionMode = Executed | Sourced deriving (Show, Eq)
 type ErrorMessage = String
 type Code = Integer
 
-data Severity = ErrorC | WarningC | InfoC | StyleC deriving (Show, Eq, Ord)
+data Severity = ErrorC | WarningC | InfoC | StyleC
+    deriving (Show, Eq, Ord, Generic, NFData)
 data Position = Position {
     posFile :: String,    -- Filename
     posLine :: Integer,   -- 1 based source line
     posColumn :: Integer  -- 1 based source column, where tabs are 8
-} deriving (Show, Eq)
+} deriving (Show, Eq, Generic, NFData)
 
 newPosition :: Position
 newPosition = Position {
@@ -188,7 +193,7 @@ data Comment = Comment {
     cSeverity :: Severity,
     cCode     :: Code,
     cMessage  :: String
-} deriving (Show, Eq)
+} deriving (Show, Eq, Generic, NFData)
 
 newComment :: Comment
 newComment = Comment {
@@ -202,7 +207,7 @@ data Replacement = Replacement {
     repStartPos :: Position,
     repEndPos :: Position,
     repString :: String
-} deriving (Show, Eq)
+} deriving (Show, Eq, Generic, NFData)
 
 newReplacement = Replacement {
     repStartPos = newPosition,
@@ -212,7 +217,7 @@ newReplacement = Replacement {
 
 data Fix = Fix {
     fixReplacements :: [Replacement]
-} deriving (Show, Eq)
+} deriving (Show, Eq, Generic, NFData)
 
 newFix = Fix {
     fixReplacements = []
@@ -223,7 +228,7 @@ data PositionedComment = PositionedComment {
     pcEndPos   :: Position,
     pcComment  :: Comment,
     pcFix      :: Maybe Fix
-} deriving (Show, Eq)
+} deriving (Show, Eq, Generic, NFData)
 
 newPositionedComment :: PositionedComment
 newPositionedComment = PositionedComment {
@@ -237,7 +242,7 @@ data TokenComment = TokenComment {
     tcId :: Id,
     tcComment :: Comment,
     tcFix :: Maybe Fix
-} deriving (Show, Eq)
+} deriving (Show, Eq, Generic, NFData)
 
 newTokenComment = TokenComment {
     tcId = Id 0,