diff --git a/src-ghc/Pact/Interpreter.hs b/src-ghc/Pact/Interpreter.hs
index e2a20ab34..1327a8692 100644
--- a/src-ghc/Pact/Interpreter.hs
+++ b/src-ghc/Pact/Interpreter.hs
@@ -128,6 +128,8 @@ data EvalResult = EvalResult
     -- ^ Details on each gas consumed/charged
   , _erEvents :: [PactEvent]
     -- ^ emitted events
+  , _erWarnings :: S.Set PactWarning
+    -- ^ emitted warning
   } deriving (Eq,Show)
 
 -- | Execute pact statements.
@@ -169,7 +171,7 @@ setupEvalEnv
   -> IO (EvalEnv e)
 setupEvalEnv dbEnv ent mode msgData refStore gasEnv np spv pd ec = do
   gasRef <- newIORef 0
-  warnRef <- newIORef []
+  warnRef <- newIORef mempty
   pure EvalEnv {
     _eeRefStore = refStore
   , _eeMsgSigs = mkMsgSigs $ mdSigners msgData
@@ -227,6 +229,7 @@ interpret runner evalEnv terms = do
   ((rs,logs,txid),state) <-
     runEval def evalEnv $ evalTerms runner terms
   gas <- readIORef (_eeGas evalEnv)
+  warnings <- readIORef (_eeWarnings evalEnv)
   let gasLogs = _evalLogGas state
       pactExec = _evalPactExec state
       modules = _rsLoadedModules $ _evalRefs state
@@ -234,7 +237,7 @@ interpret runner evalEnv terms = do
   return $! EvalResult
     terms
     (map (elideModRefInfo . toPactValueLenient) rs)
-    logs pactExec gas modules txid gasLogs (_evalEvents state)
+    logs pactExec gas modules txid gasLogs (_evalEvents state) warnings
 
 evalTerms :: Interpreter e -> EvalInput -> Eval e EvalOutput
 evalTerms interp input = withRollback (start (interpreter interp runInput) >>= end)
diff --git a/src/Pact/Repl.hs b/src/Pact/Repl.hs
index 360f15f44..744df80bd 100644
--- a/src/Pact/Repl.hs
+++ b/src/Pact/Repl.hs
@@ -132,7 +132,7 @@ initEvalEnv :: LibState -> IO (EvalEnv LibState)
 initEvalEnv ls = do
   mv <- newMVar ls
   gasRef <- newIORef 0
-  warnRef <- newIORef []
+  warnRef <- newIORef mempty
   return $ EvalEnv
     { _eeRefStore = RefStore nativeDefs
     , _eeMsgSigs = mempty
@@ -248,7 +248,7 @@ pureEval ei e = do
         wref <- use (rEnv . eeWarnings)
         warnings <- liftIO $ readIORef wref
         traverse_ (outStrLn HOut . renderCompactString) warnings
-        liftIO $ writeIORef wref []
+        liftIO $ writeIORef wref mempty
         doOut ei mode a
         rEvalState .= es
         updateForOp ei a
diff --git a/src/Pact/Types/Runtime.hs b/src/Pact/Types/Runtime.hs
index b467c612f..496aa9af0 100644
--- a/src/Pact/Types/Runtime.hs
+++ b/src/Pact/Types/Runtime.hs
@@ -74,6 +74,7 @@ import qualified Data.Map.Strict as M
 import qualified Data.Set as S
 import Data.String
 import Data.Text (Text,pack)
+import Data.Set(Set)
 import GHC.Generics (Generic)
 
 import Pact.Types.Capability
@@ -125,7 +126,7 @@ data PactWarning
   = DeprecatedNative NativeDefName Text
   -- | Deprecated overload with help message
   | DeprecatedOverload NativeDefName Text
-  deriving (Show)
+  deriving (Show, Eq, Ord)
 
 instance Pretty PactWarning where
   pretty = \case
@@ -246,7 +247,7 @@ data EvalEnv e = EvalEnv {
       -- | Are we in the repl? If not, ignore info
     , _eeInRepl :: Bool
       -- | Warnings ref
-    , _eeWarnings :: IORef [PactWarning]
+    , _eeWarnings :: IORef (Set PactWarning)
     }
 makeLenses ''EvalEnv
 
@@ -364,7 +365,7 @@ method i f = do
 
 emitPactWarning :: PactWarning -> Eval e ()
 emitPactWarning pw =
-  view eeWarnings >>= \e -> liftIO (modifyIORef' e (pw:))
+  view eeWarnings >>= \e -> liftIO (modifyIORef' e (S.insert pw))
 --
 -- Methods for invoking backend function-record function.
 --