diff --git a/CHANGELOG.md b/CHANGELOG.md
index fb0618226..13b8b2c3a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - #1149, OpenAPI: Change `GET` response type to array - @laughedelic
 - #1152, Fix RPC failing when having arguments with reserved or uppercase keywords - @mdr1384
 - #905, Fix intermittent empty replies - @steve-chavez
+- #1139, Fix JWTIssuedAtFuture failure for valid iat claim - @steve-chavez
 
 ### Changed
 
diff --git a/src/PostgREST/Auth.hs b/src/PostgREST/Auth.hs
index f18cf317b..43f249435 100644
--- a/src/PostgREST/Auth.hs
+++ b/src/PostgREST/Auth.hs
@@ -20,6 +20,7 @@ module PostgREST.Auth (
   ) where
 
 import           Control.Lens.Operators
+import           Control.Lens           (set)
 import qualified Data.Aeson             as JSON
 import qualified Data.HashMap.Strict    as M
 import           Data.Time.Clock        (UTCTime)
@@ -48,7 +49,7 @@ jwtClaims secret audience payload time jspath =
   case secret of
     Nothing -> return JWTMissingSecret
     Just s -> do
-      let validation = defaultJWTValidationSettings (maybe (const True) (==) audience)
+      let validation = set allowedSkew 1 $ defaultJWTValidationSettings (maybe (const True) (==) audience)
       eJwt <- runExceptT $ do
         jwt <- decodeCompact payload
         verifyClaimsAt validation s time jwt
diff --git a/test/io-tests.sh b/test/io-tests.sh
index 90bdd0395..b11f13a16 100755
--- a/test/io-tests.sh
+++ b/test/io-tests.sh
@@ -120,6 +120,29 @@ invalidRoleClaimKey(){
   pgrStop
 }
 
+# ensure iat claim is successful in the presence of pgrst time cache, see https://github.com/PostgREST/postgrest/issues/1139
+ensureIatClaimWorks(){
+  pgrStart "./configs/simple.config"
+  while pgrStarted && test "$( rootStatus )" -ne 200
+  do
+    # wait for the server to start
+    sleep 0.1 \
+    || sleep 1 # fallback: subsecond sleep is not standard and may fail
+  done
+  for i in {1..10}; do \
+    iatJwt=$(psql -qtAX postgrest_test -c "select jwt.sign(row_to_json(r), 'reallyreallyreallyreallyverysafe') from ( select 'postgrest_test_author' as role, extract(epoch from now()) as iat) r")
+    httpStatus="$( authorsStatus $iatJwt )"
+    if test "$httpStatus" -ne 200
+    then
+      ko "iat claim rejected with $httpStatus"
+      return
+    fi
+    sleep .5;\
+  done
+  ok "accepted iat claim"
+  pgrStop
+}
+
 # PRE: curl must be available
 test -n "$(command -v curl)" || bailOut 'curl is not available'
 
@@ -157,6 +180,8 @@ invalidRoleClaimKey '.#$%&$%/'
 invalidRoleClaimKey ''
 invalidRoleClaimKey 1234
 
+ensureIatClaimWorks
+
 cleanUp
 
 exit $failedTests
diff --git a/test/io-tests/configs/simple.config b/test/io-tests/configs/simple.config
new file mode 100644
index 000000000..350cb7e71
--- /dev/null
+++ b/test/io-tests/configs/simple.config
@@ -0,0 +1,7 @@
+db-uri = "postgres:///postgrest_test"
+db-schema = "test"
+db-anon-role = "postgrest_test_anonymous"
+db-pool = 1
+server-host = "127.0.0.1"
+server-port = 49421
+jwt-secret = "reallyreallyreallyreallyverysafe"