diff --git a/src/SystemVariableAssigner.php b/src/SystemVariableAssigner.php
index a928ac3..2e631c7 100644
--- a/src/SystemVariableAssigner.php
+++ b/src/SystemVariableAssigner.php
@@ -3,6 +3,7 @@
 namespace Mpyw\LaravelMySqlSystemVariableManager;
 
 use Closure;
+use Mpyw\LaravelMySqlSystemVariableManager\Value as BindingValue;
 use Mpyw\LaravelPdoEmulationControl\EmulationController;
 use Mpyw\Unclosure\Value;
 use PDO;
@@ -86,7 +87,8 @@ protected static function withStatementFor(PDO $pdo, string $query, array $value
     {
         $statement = $pdo->prepare($query);
         foreach (array_values($values) as $i => $value) {
-            $statement->bindValue($i + 1, $value, Grammar::paramTypeFor($value));
+            $value = BindingValue::wrap($value);
+            $statement->bindValue($i + 1, $value->getValue(), $value->getParamType());
         }
         $statement->execute();
 
diff --git a/src/SystemVariableGrammar.php b/src/SystemVariableGrammar.php
index b51ecb9..16f5b5e 100644
--- a/src/SystemVariableGrammar.php
+++ b/src/SystemVariableGrammar.php
@@ -2,8 +2,6 @@
 
 namespace Mpyw\LaravelMySqlSystemVariableManager;
 
-use PDO;
-
 class SystemVariableGrammar
 {
     /**
@@ -23,42 +21,11 @@ public static function assignmentExpressions(array $values): array
     {
         $expressions = [];
         foreach ($values as $name => $value) {
-            $expressions[] = static::escapeIdentifier($name) . '=' . static::placeholderFor($value);
+            $expressions[] = static::escapeIdentifier($name) . '=' . Value::wrap($value)->getPlaceholder();
         }
         return $expressions;
     }
 
-    /**
-     * @param  mixed $value
-     * @return int
-     */
-    public static function paramTypeFor($value): int
-    {
-        switch (gettype($value)) {
-            case 'integer':
-                return PDO::PARAM_INT;
-            case 'boolean':
-                return PDO::PARAM_BOOL;
-            case 'NULL':
-            default:
-                return PDO::PARAM_STR;
-        }
-    }
-
-    /**
-     * @param  mixed  $value
-     * @return string
-     */
-    public static function placeholderFor($value): string
-    {
-        switch (gettype($value)) {
-            case 'double':
-                return 'cast(? as decimal(65, 30))';
-            default:
-                return '?';
-        }
-    }
-
     /**
      * @param  string $identifier
      * @return string
diff --git a/src/Value.php b/src/Value.php
new file mode 100644
index 0000000..b6feca8
--- /dev/null
+++ b/src/Value.php
@@ -0,0 +1,172 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager;
+
+use InvalidArgumentException;
+use PDO;
+
+class Value implements ValueInterface
+{
+    /**
+     * @var mixed
+     */
+    protected $value;
+
+    /**
+     * @var string
+     */
+    protected $type;
+
+    /**
+     * Create new int value for MySQL system variable.
+     *
+     * @param  int    $value
+     * @return static
+     */
+    public static function int(int $value)
+    {
+        return new static($value, static::TYPE_INT);
+    }
+
+    /**
+     * Create new bool value for MySQL system variable.
+     *
+     * @param  bool   $value
+     * @return static
+     */
+    public static function bool(bool $value)
+    {
+        return new static($value, static::TYPE_BOOL);
+    }
+
+    /**
+     * Create new float value for MySQL system variable.
+     *
+     * @param  float  $value
+     * @return static
+     */
+    public static function float(float $value)
+    {
+        return new static($value, static::TYPE_FLOAT);
+    }
+
+    /**
+     * Create new string value for MySQL system variable.
+     *
+     * @param  string $value
+     * @return static
+     */
+    public static function str(string $value)
+    {
+        return new static($value, static::TYPE_STR);
+    }
+
+    /**
+     * Create new typed value for MySQL system variable.
+     *
+     * @param  string                                                 $type
+     * @param  bool|float|int|string                                  $value
+     * @return \Mpyw\LaravelMySqlSystemVariableManager\ValueInterface
+     */
+    public static function as(string $type, $value): ValueInterface
+    {
+        switch ($type) {
+            case static::TYPE_INT:
+                return static::int($value);
+            case static::TYPE_BOOL:
+                return static::bool($value);
+            case static::TYPE_FLOAT:
+                return static::float($value);
+            case static::TYPE_STR:
+                return static::str($value);
+            default:
+                throw new InvalidArgumentException('The type must be one of "integer", "boolean", "double" or "string".');
+        }
+    }
+
+    /**
+     * Automatically wrap a non-null value.
+     *
+     * @param  mixed                                                  $value
+     * @return \Mpyw\LaravelMySqlSystemVariableManager\ValueInterface
+     */
+    public static function wrap($value): ValueInterface
+    {
+        if ($value instanceof ValueInterface) {
+            return $value;
+        }
+        if (is_scalar($value)) {
+            return static::as(gettype($value), $value);
+        }
+        throw new InvalidArgumentException('The value must be a scalar or ' . ValueInterface::class . ' instance.');
+    }
+
+    /**
+     * Value constructor.
+     *
+     * @param mixed  $value
+     * @param string $type
+     */
+    protected function __construct($value, string $type)
+    {
+        $this->value = $value;
+        $this->type = $type;
+    }
+
+    /**
+     * Return original value.
+     *
+     * @return bool|float|int|string
+     */
+    public function getValue()
+    {
+        return $this->value;
+    }
+
+    /**
+     * Return type.
+     *
+     * @return string
+     */
+    public function getType(): string
+    {
+        return $this->type;
+    }
+
+    /**
+     * Return PDO::PARAM_* type.
+     *
+     * @return int
+     */
+    public function getParamType(): int
+    {
+        switch ($this->type) {
+            case static::TYPE_INT:
+                return PDO::PARAM_INT;
+            case static::TYPE_BOOL:
+                return PDO::PARAM_BOOL;
+            case static::TYPE_FLOAT:
+            case static::TYPE_STR:
+            default:
+                return PDO::PARAM_STR;
+        }
+    }
+
+    /**
+     * Return a placeholder format.
+     *
+     * @return string
+     */
+    public function getPlaceholder(): string
+    {
+        switch ($this->type) {
+            case static::TYPE_FLOAT:
+                return 'cast(? as decimal(65, 30))';
+            case static::TYPE_INT:
+            case static::TYPE_BOOL:
+            case static::TYPE_STR:
+            default:
+                return '?';
+        }
+    }
+}
diff --git a/src/ValueInterface.php b/src/ValueInterface.php
new file mode 100644
index 0000000..6d880e3
--- /dev/null
+++ b/src/ValueInterface.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager;
+
+interface ValueInterface
+{
+    public const TYPE_INT = 'integer';
+    public const TYPE_BOOL = 'boolean';
+    public const TYPE_FLOAT = 'double';
+    public const TYPE_STR = 'string';
+
+    /**
+     * Return original value.
+     *
+     * @return bool|float|int|string
+     */
+    public function getValue();
+
+    /**
+     * Return type.
+     *
+     * @return string
+     */
+    public function getType(): string;
+
+    /**
+     * Return PDO::PARAM_* type.
+     *
+     * @return int
+     */
+    public function getParamType(): int;
+
+    /**
+     * Return placeholder for prepared statement.
+     *
+     * @return string
+     */
+    public function getPlaceholder(): string;
+}
diff --git a/tests/BasicVariableAssignmentTest.php b/tests/BasicVariableAssignmentTest.php
index 58d53ac..f992ab6 100644
--- a/tests/BasicVariableAssignmentTest.php
+++ b/tests/BasicVariableAssignmentTest.php
@@ -2,8 +2,9 @@
 
 namespace Mpyw\LaravelMySqlSystemVariableManager\Tests;
 
+use InvalidArgumentException;
 use Mpyw\LaravelMySqlSystemVariableManager\MySqlConnection;
-use PDOException;
+use Mpyw\LaravelMySqlSystemVariableManager\Value;
 
 class BasicVariableAssignmentTest extends TestCase
 {
@@ -39,13 +40,21 @@ public function provideBasicVariables(): array
             'assigning boolean (emulated)' => ['foreign_key_checks', true, '1', false, '0'],
             'assigning string (native)' => ['tx_isolation', false, 'REPEATABLE-READ', 'read-committed', 'READ-COMMITTED'],
             'assigning string (emulated)' => ['tx_isolation', true, 'REPEATABLE-READ', 'read-committed', 'READ-COMMITTED'],
+            'assigning wrapped float (native)' => ['long_query_time', false, 10.0, Value::float(15.0), 15.0],
+            'assigning wrapped float (emulated)' => ['long_query_time', true, '10.000000', Value::float(15.0), '15.000000'],
+            'assigning wrapped integer (native)' => ['long_query_time', false, 10.0, Value::int(15), 15.0],
+            'assigning wrapped integer (emulated)' => ['long_query_time', true, '10.000000', Value::int(15), '15.000000'],
+            'assigning wrapped boolean (native)' => ['foreign_key_checks', false, 1, Value::bool(false), 0],
+            'assigning wrapped boolean (emulated)' => ['foreign_key_checks', true, '1', Value::bool(false), '0'],
+            'assigning wrapped string (native)' => ['tx_isolation', false, 'REPEATABLE-READ', Value::str('read-committed'), 'READ-COMMITTED'],
+            'assigning wrapped string (emulated)' => ['tx_isolation', true, 'REPEATABLE-READ', Value::str('read-committed'), 'READ-COMMITTED'],
         ];
     }
 
     public function testAssigningNullThrowsExceptionOnNative(): void
     {
-        $this->expectException(PDOException::class);
-        $this->expectExceptionMessage("SQLSTATE[42000]: Syntax error or access violation: 1231 Variable 'foreign_key_checks' can't be set to the value of 'NULL'");
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The value must be a scalar or Mpyw\LaravelMySqlSystemVariableManager\ValueInterface instance.');
 
         $this->onNativeConnection(function (MySqlConnection $db) {
             $db->setSystemVariable('foreign_key_checks', null);
@@ -55,8 +64,8 @@ public function testAssigningNullThrowsExceptionOnNative(): void
 
     public function testAssigningNullThrowsExceptionOnEmulation(): void
     {
-        $this->expectException(PDOException::class);
-        $this->expectExceptionMessage("SQLSTATE[42000]: Syntax error or access violation: 1231 Variable 'foreign_key_checks' can't be set to the value of 'NULL'");
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The value must be a scalar or Mpyw\LaravelMySqlSystemVariableManager\ValueInterface instance.');
 
         $this->onEmulatedConnection(function (MySqlConnection $db) {
             $db->setSystemVariable('foreign_key_checks', null);
@@ -64,15 +73,24 @@ public function testAssigningNullThrowsExceptionOnEmulation(): void
         });
     }
 
-    public function testAssigningNullDoesNotThrowOnUnresolvedConnection(): void
+    public function testAssigningNullThrowsOnUnresolvedNativeConnection(): void
     {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The value must be a scalar or Mpyw\LaravelMySqlSystemVariableManager\ValueInterface instance.');
+
         $this->onNativeConnection(function (MySqlConnection $db) {
             $db->setSystemVariable('foreign_key_checks', null);
         });
+    }
+
+    public function testAssigningNullThrowsOnUnresolvedEmulatedConnection(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The value must be a scalar or Mpyw\LaravelMySqlSystemVariableManager\ValueInterface instance.');
+
         $this->onEmulatedConnection(function (MySqlConnection $db) {
             $db->setSystemVariable('foreign_key_checks', null);
         });
-        $this->assertTrue(true);
     }
 
     public function testAssignmentPriorityOnLazilyResolvedConnection(): void