diff --git a/src/Type/Definition/FloatType.php b/src/Type/Definition/FloatType.php
index d5de717..0c8853a 100644
--- a/src/Type/Definition/FloatType.php
+++ b/src/Type/Definition/FloatType.php
@@ -1,8 +1,8 @@
 <?php
 namespace GraphQL\Type\Definition;
 
+use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
-use GraphQL\Error\UserError;
 use GraphQL\Language\AST\FloatValueNode;
 use GraphQL\Language\AST\IntValueNode;
 use GraphQL\Utils\Utils;
@@ -63,7 +63,7 @@ values as specified by
                 $isInput ? Utils::printSafeJson($value) : Utils::printSafe($value)
             );
         }
-        throw ($isInput ? new UserError($err) : new InvariantViolation($err));
+        throw ($isInput ? new Error($err) : new InvariantViolation($err));
     }
 
     /**
diff --git a/src/Type/Definition/IDType.php b/src/Type/Definition/IDType.php
index a41eb22..594bea9 100644
--- a/src/Type/Definition/IDType.php
+++ b/src/Type/Definition/IDType.php
@@ -1,8 +1,8 @@
 <?php
 namespace GraphQL\Type\Definition;
 
+use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
-use GraphQL\Error\UserError;
 use GraphQL\Language\AST\IntValueNode;
 use GraphQL\Language\AST\StringValueNode;
 use GraphQL\Utils\Utils;
@@ -65,7 +65,7 @@ When expected as an input type, any string (such as `"4"`) or integer
             return 'null';
         }
         if (!is_scalar($value)) {
-            throw new UserError("ID type cannot represent non scalar value: " . Utils::printSafeJson($value));
+            throw new Error("ID type cannot represent non scalar value: " . Utils::printSafeJson($value));
         }
         return (string) $value;
     }
diff --git a/src/Type/Definition/IntType.php b/src/Type/Definition/IntType.php
index 35e66e4..4e797df 100644
--- a/src/Type/Definition/IntType.php
+++ b/src/Type/Definition/IntType.php
@@ -1,8 +1,8 @@
 <?php
 namespace GraphQL\Type\Definition;
 
+use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
-use GraphQL\Error\UserError;
 use GraphQL\Language\AST\IntValueNode;
 use GraphQL\Utils\Utils;
 
@@ -57,7 +57,7 @@ values. Int can represent values between -(2^31) and 2^31 - 1. ';
      */
     private function coerceInt($value, $isInput)
     {
-        $errClass = $isInput ? UserError::class : InvariantViolation::class;
+        $errClass = $isInput ? Error::class : InvariantViolation::class;
 
         if ($value === '') {
             throw new $errClass(
diff --git a/src/Type/Definition/ObjectType.php b/src/Type/Definition/ObjectType.php
index 43a743f..2d299f9 100644
--- a/src/Type/Definition/ObjectType.php
+++ b/src/Type/Definition/ObjectType.php
@@ -1,7 +1,7 @@
 <?php
 namespace GraphQL\Type\Definition;
+use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
-use GraphQL\Error\UserError;
 use GraphQL\Utils\Utils;
 
 
@@ -133,7 +133,7 @@ class ObjectType extends Type implements OutputType, CompositeType
             $this->getFields();
         }
         if (!isset($this->fields[$name])) {
-            throw new UserError(sprintf("Field '%s' is not defined for type '%s'", $name, $this->name));
+            throw new Error(sprintf("Field '%s' is not defined for type '%s'", $name, $this->name));
         }
         return $this->fields[$name];
     }
diff --git a/src/Type/Definition/StringType.php b/src/Type/Definition/StringType.php
index 7b82481..46bc942 100644
--- a/src/Type/Definition/StringType.php
+++ b/src/Type/Definition/StringType.php
@@ -1,8 +1,8 @@
 <?php
 namespace GraphQL\Type\Definition;
 
+use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
-use GraphQL\Error\UserError;
 use GraphQL\Language\AST\StringValueNode;
 use GraphQL\Utils\Utils;
 
@@ -62,7 +62,7 @@ represent free-form human-readable text.';
             return 'null';
         }
         if (!is_scalar($value)) {
-            throw new UserError("String cannot represent non scalar value: " . Utils::printSafe($value));
+            throw new Error("String cannot represent non scalar value: " . Utils::printSafe($value));
         }
         return (string) $value;
     }