diff --git a/src/Executor/Values.php b/src/Executor/Values.php
index 441dd04..e3f6023 100644
--- a/src/Executor/Values.php
+++ b/src/Executor/Values.php
@@ -248,7 +248,7 @@ class Values
                 // a non-null value.
                 $parseResult = $type->parseValue($value);
                 if (null === $parseResult) {
-                    $v = json_encode($value);
+                    $v = Utils::printSafe($value);
                     return [
                         "Expected type \"{$type->name}\", found $v."
                     ];
@@ -256,10 +256,12 @@ class Values
                 return [];
             } catch (\Exception $e) {
                 return [
+                    "Expected type \"{$type->name}\", found " . Utils::printSafe($value) . ': ' .
                     $e->getMessage()
                 ];
             } catch (\Throwable $e) {
                 return [
+                    "Expected type \"{$type->name}\", found " . Utils::printSafe($value) . ': ' .
                     $e->getMessage()
                 ];
             }
diff --git a/src/Utils.php b/src/Utils.php
index 679e5d2..45b10a0 100644
--- a/src/Utils.php
+++ b/src/Utils.php
@@ -253,6 +253,9 @@ class Utils
         if ('' === $var) {
             return '(empty string)';
         }
+        if (is_string($var)) {
+            return "\"$var\"";
+        }
         if (is_scalar($var)) {
             return (string) $var;
         }
diff --git a/tests/Type/EnumTypeTest.php b/tests/Type/EnumTypeTest.php
index 587f195..126d5b7 100644
--- a/tests/Type/EnumTypeTest.php
+++ b/tests/Type/EnumTypeTest.php
@@ -236,7 +236,7 @@ class EnumTypeTest extends \PHPUnit_Framework_TestCase
             '{ colorEnum(fromString: "GREEN") }',
             null,
             [
-                'message' => 'Expected a value of type "Color" but received: GREEN',
+                'message' => 'Expected a value of type "Color" but received: "GREEN"',
                 'locations' => [new SourceLocation(1, 3)]
             ]
         );
@@ -447,7 +447,7 @@ class EnumTypeTest extends \PHPUnit_Framework_TestCase
             [
                 'data' => ['first' => 'ONE', 'second' => 'TWO', 'third' => null],
                 'errors' => [[
-                    'message' => 'Expected a value of type "SimpleEnum" but received: WRONG',
+                    'message' => 'Expected a value of type "SimpleEnum" but received: "WRONG"',
                     'locations' => [['line' => 4, 'column' => 13]]
                 ]]
             ],
diff --git a/tests/Type/ScalarSerializationTest.php b/tests/Type/ScalarSerializationTest.php
index b097a10..23165d7 100644
--- a/tests/Type/ScalarSerializationTest.php
+++ b/tests/Type/ScalarSerializationTest.php
@@ -59,7 +59,7 @@ class ScalarSerializationTest extends \PHPUnit_Framework_TestCase
             $intType->serialize('one');
             $this->fail('Expected exception was not thrown');
         } catch (UserError $e) {
-            $this->assertEquals('Int cannot represent non 32-bit signed integer value: one', $e->getMessage());
+            $this->assertEquals('Int cannot represent non 32-bit signed integer value: "one"', $e->getMessage());
         }
 
         try {
@@ -93,7 +93,7 @@ class ScalarSerializationTest extends \PHPUnit_Framework_TestCase
             $floatType->serialize('one');
             $this->fail('Expected exception was not thrown');
         } catch (UserError $e) {
-            $this->assertEquals('Float cannot represent non numeric value: one', $e->getMessage());
+            $this->assertEquals('Float cannot represent non numeric value: "one"', $e->getMessage());
         }
 
         try {