diff --git a/src/Database/PostgreSQL.js b/src/Database/PostgreSQL.js
index e48d74f..3007fba 100644
--- a/src/Database/PostgreSQL.js
+++ b/src/Database/PostgreSQL.js
@@ -37,10 +37,10 @@ exports.ffiUnsafeQuery = function(client) {
                         text: sql,
                         values: values,
                         rowMode: 'array',
-                    }).catch(function(err) {
-                        onError(err);
                     }).then(function(result) {
                         onSuccess(result.rows);
+                    }).catch(function(err) {
+                        onError(err);
                     });
 
                 return function (cancelError, cancelerError, cancelerSuccess) {
diff --git a/test/Main.purs b/test/Main.purs
index e89f920..17ff9ec 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -10,6 +10,7 @@ import Data.Array (zip)
 import Data.Date (Date, canonicalDate)
 import Data.DateTime.Instant (Instant, unInstant)
 import Data.Decimal as D
+import Data.Either (isLeft)
 import Data.Enum (toEnum)
 import Data.Foldable (all, length)
 import Data.JSDate (JSDate, jsdate, toInstant)
@@ -169,6 +170,15 @@ main = void $ launchAff do
           """) Row0
           liftEffect <<< assert $ sauerkrautPrice == [Row1 (D.fromString "3.30")]
 
+        test conn "constraint failure" $ do
+          withTransaction conn $ do
+            result <- try $ execute conn (Query """
+              INSERT INTO foods (name)
+              VALUES ($1)
+            """) (Row1 "pork")
+            liftEffect <<< assert $ isLeft result
+          testCount 0
+
         test conn "handling date value" $ do
           let
             d1 = date 2010 2 31