diff --git a/src/Internal/Serde/SerdeInt64.php b/src/Internal/Serde/SerdeInt64.php
index a3e5993..dab8836 100644
--- a/src/Internal/Serde/SerdeInt64.php
+++ b/src/Internal/Serde/SerdeInt64.php
@@ -10,8 +10,8 @@
 
 /**
  * @internal
- * @template-implements SerializeValue<Number>
- * @template-implements DeserializeValue<Number>
+ * @template-implements SerializeValue<int>
+ * @template-implements DeserializeValue<int>
  */
 enum SerdeInt64 implements
     SerializeValue,
@@ -30,7 +30,7 @@ public function serialize(WriteBuffer $buffer, mixed $value): void
         static $p63;
         $p63 ??= new Number(2)->pow(63);
 
-        $num = $value->mod($p64);
+        $num = new Number($value)->mod($p64);
 
         if ($num->compare($p63) >= 0) {
             $num -= $p64;
@@ -44,7 +44,7 @@ public function serialize(WriteBuffer $buffer, mixed $value): void
     }
 
     #[\Override]
-    public function deserialize(ReadBuffer $buffer): Number
+    public function deserialize(ReadBuffer $buffer): int
     {
         /** @var ?Number $p63 */
         static $p63;
@@ -61,6 +61,6 @@ public function deserialize(ReadBuffer $buffer): Number
             $num -= $p64;
         }
 
-        return $num;
+        return (int) $num->value;
     }
 }
diff --git a/src/Internal/Serde/SerdeSFixed64.php b/src/Internal/Serde/SerdeSFixed64.php
index 40e31cf..4f90719 100644
--- a/src/Internal/Serde/SerdeSFixed64.php
+++ b/src/Internal/Serde/SerdeSFixed64.php
@@ -11,8 +11,8 @@
 
 /**
  * @internal
- * @template-implements SerializeValue<Number>
- * @template-implements DeserializeValue<Number>
+ * @template-implements SerializeValue<int>
+ * @template-implements DeserializeValue<int>
  */
 enum SerdeSFixed64 implements
     SerializeValue,
@@ -23,12 +23,12 @@ enum SerdeSFixed64 implements
     #[\Override]
     public function serialize(WriteBuffer $buffer, mixed $value): void
     {
-        $buffer->write(Endian\Order::Little->packInt64($value));
+        $buffer->write(Endian\Order::Little->packInt64(new Number($value)));
     }
 
     #[\Override]
-    public function deserialize(ReadBuffer $buffer): Number
+    public function deserialize(ReadBuffer $buffer): int
     {
-        return Endian\Order::Little->unpackInt64($buffer->read(8));
+        return (int) Endian\Order::Little->unpackInt64($buffer->read(8))->value;
     }
 }
diff --git a/src/Internal/Serde/SerdeSInt32.php b/src/Internal/Serde/SerdeSInt32.php
index 590084d..0f1cfaf 100644
--- a/src/Internal/Serde/SerdeSInt32.php
+++ b/src/Internal/Serde/SerdeSInt32.php
@@ -37,7 +37,7 @@ public function serialize(WriteBuffer $buffer, mixed $value): void
             $num -= $p32;
         }
 
-        SerdeSInt64::T->serialize($buffer, $num);
+        SerdeSInt64::T->serialize($buffer, (int) $num->value);
     }
 
     #[\Override]
@@ -51,8 +51,7 @@ public function deserialize(ReadBuffer $buffer): int
         static $p32;
         $p32 ??= new Number(2)->pow(32);
 
-        $num = SerdeSInt64::T->deserialize($buffer);
-        $num = $num->mod($p32);
+        $num = new Number(SerdeSInt64::T->deserialize($buffer))->mod($p32);
 
         if ($num->compare($p31) >= 0) {
             $num -= $p32;
diff --git a/src/Internal/Serde/SerdeSInt64.php b/src/Internal/Serde/SerdeSInt64.php
index 136b905..7f4c10f 100644
--- a/src/Internal/Serde/SerdeSInt64.php
+++ b/src/Internal/Serde/SerdeSInt64.php
@@ -11,8 +11,8 @@
 
 /**
  * @internal
- * @template-implements SerializeValue<Number>
- * @template-implements DeserializeValue<Number>
+ * @template-implements SerializeValue<int>
+ * @template-implements DeserializeValue<int>
  */
 enum SerdeSInt64 implements
     SerializeValue,
@@ -23,12 +23,12 @@ enum SerdeSInt64 implements
     #[\Override]
     public function serialize(WriteBuffer $buffer, mixed $value): void
     {
-        SerdeVarint::T->serialize($buffer, Varint\BcMath::Codec->encodeZigZag($value));
+        SerdeVarint::T->serialize($buffer, Varint\BcMath::Codec->encodeZigZag(new Number($value)));
     }
 
     #[\Override]
-    public function deserialize(ReadBuffer $buffer): Number
+    public function deserialize(ReadBuffer $buffer): int
     {
-        return Varint\BcMath::Codec->decodeZigZag(SerdeVarint::T->deserialize($buffer));
+        return (int) Varint\BcMath::Codec->decodeZigZag(SerdeVarint::T->deserialize($buffer))->value;
     }
 }
diff --git a/src/Reflection/Int64T.php b/src/Reflection/Int64T.php
index 66e2ea9..da00e06 100644
--- a/src/Reflection/Int64T.php
+++ b/src/Reflection/Int64T.php
@@ -4,11 +4,9 @@
 
 namespace Thesis\Protobuf\Reflection;
 
-use BcMath\Number;
-
 /**
  * @api
- * @template-implements Type<Number>
+ * @template-implements Type<int>
  */
 enum Int64T implements Type
 {
diff --git a/src/Reflection/Internal/Visitor/ToValueTypeVisitor.php b/src/Reflection/Internal/Visitor/ToValueTypeVisitor.php
index 6e46433..d2e56b4 100644
--- a/src/Reflection/Internal/Visitor/ToValueTypeVisitor.php
+++ b/src/Reflection/Internal/Visitor/ToValueTypeVisitor.php
@@ -14,12 +14,15 @@
 use Thesis\Protobuf\Reflection\Fixed32T;
 use Thesis\Protobuf\Reflection\FloatT;
 use Thesis\Protobuf\Reflection\Int32T;
+use Thesis\Protobuf\Reflection\Int64T;
 use Thesis\Protobuf\Reflection\ListT;
 use Thesis\Protobuf\Reflection\MapT;
 use Thesis\Protobuf\Reflection\ObjectT;
 use Thesis\Protobuf\Reflection\Reflector;
 use Thesis\Protobuf\Reflection\SFixed32T;
+use Thesis\Protobuf\Reflection\SFixed64T;
 use Thesis\Protobuf\Reflection\SInt32T;
+use Thesis\Protobuf\Reflection\SInt64T;
 use Thesis\Protobuf\Reflection\StringT;
 use Thesis\Protobuf\Reflection\Type;
 use Thesis\Protobuf\Reflection\Uint32T;
@@ -100,6 +103,30 @@ public function sfixed32(SFixed32T $type): mixed
         return $this->value;
     }
 
+    #[\Override]
+    public function int64(Int64T $type): mixed
+    {
+        \assert(\is_int($this->value));
+
+        return $this->value;
+    }
+
+    #[\Override]
+    public function sint64(SInt64T $type): mixed
+    {
+        \assert(\is_int($this->value));
+
+        return $this->value;
+    }
+
+    #[\Override]
+    public function sfixed64(SFixed64T $type): mixed
+    {
+        \assert(\is_int($this->value));
+
+        return $this->value;
+    }
+
     #[\Override]
     public function string(StringT $type): mixed
     {
diff --git a/src/Reflection/SFixed64T.php b/src/Reflection/SFixed64T.php
index 6712bae..19ceb63 100644
--- a/src/Reflection/SFixed64T.php
+++ b/src/Reflection/SFixed64T.php
@@ -4,11 +4,9 @@
 
 namespace Thesis\Protobuf\Reflection;
 
-use BcMath\Number;
-
 /**
  * @api
- * @template-implements Type<Number>
+ * @template-implements Type<int>
  */
 enum SFixed64T implements Type
 {
diff --git a/src/Reflection/SInt64T.php b/src/Reflection/SInt64T.php
index c9e8061..bc9b11b 100644
--- a/src/Reflection/SInt64T.php
+++ b/src/Reflection/SInt64T.php
@@ -4,11 +4,9 @@
 
 namespace Thesis\Protobuf\Reflection;
 
-use BcMath\Number;
-
 /**
  * @api
- * @template-implements Type<Number>
+ * @template-implements Type<int>
  */
 enum SInt64T implements Type
 {
diff --git a/src/Type/Int64T.php b/src/Type/Int64T.php
index baa2b1d..ede2e5b 100644
--- a/src/Type/Int64T.php
+++ b/src/Type/Int64T.php
@@ -4,18 +4,17 @@
 
 namespace Thesis\Protobuf\Type;
 
-use BcMath\Number;
 use Thesis\Protobuf\Type;
 
 /**
- * @template-implements Type<Number>
- * @template-implements Listable<Number>
+ * @template-implements Type<int>
+ * @template-implements Listable<int>
  */
 enum Int64T implements
     Type,
     Listable
 {
-    /** @use Listed<Number> */
+    /** @use Listed<int> */
     use Listed;
 
     case T;
diff --git a/src/Type/SFixed64T.php b/src/Type/SFixed64T.php
index ec1545e..67581d5 100644
--- a/src/Type/SFixed64T.php
+++ b/src/Type/SFixed64T.php
@@ -4,18 +4,17 @@
 
 namespace Thesis\Protobuf\Type;
 
-use BcMath\Number;
 use Thesis\Protobuf\Type;
 
 /**
- * @template-implements Type<Number>
- * @template-implements Listable<Number>
+ * @template-implements Type<int>
+ * @template-implements Listable<int>
  */
 enum SFixed64T implements
     Type,
     Listable
 {
-    /** @use Listed<Number> */
+    /** @use Listed<int> */
     use Listed;
 
     case T;
diff --git a/src/Type/SInt64T.php b/src/Type/SInt64T.php
index d1cd40b..556c034 100644
--- a/src/Type/SInt64T.php
+++ b/src/Type/SInt64T.php
@@ -4,18 +4,17 @@
 
 namespace Thesis\Protobuf\Type;
 
-use BcMath\Number;
 use Thesis\Protobuf\Type;
 
 /**
- * @template-implements Type<Number>
- * @template-implements Listable<Number>
+ * @template-implements Type<int>
+ * @template-implements Listable<int>
  */
 enum SInt64T implements
     Type,
     Listable
 {
-    /** @use Listed<Number> */
+    /** @use Listed<int> */
     use Listed;
 
     case T;
diff --git a/src/Value.php b/src/Value.php
index 02ceb98..808a72e 100644
--- a/src/Value.php
+++ b/src/Value.php
@@ -29,9 +29,9 @@ public static function int32(int $num): self
     }
 
     /**
-     * @return self<Number>
+     * @return self<int>
      */
-    public static function int64(Number $num): self
+    public static function int64(int $num): self
     {
         return new self($num, int64T);
     }
@@ -61,9 +61,9 @@ public static function sint32(int $num): self
     }
 
     /**
-     * @return self<Number>
+     * @return self<int>
      */
-    public static function sint64(Number $num): self
+    public static function sint64(int $num): self
     {
         return new self($num, sint64T);
     }
@@ -93,9 +93,9 @@ public static function fixed64(Number $num): self
     }
 
     /**
-     * @return self<Number>
+     * @return self<int>
      */
-    public static function sfixed64(Number $num): self
+    public static function sfixed64(int $num): self
     {
         return new self($num, sfixed64T);
     }
diff --git a/src/constructors.php b/src/constructors.php
index 31c0796..9952568 100644
--- a/src/constructors.php
+++ b/src/constructors.php
@@ -52,9 +52,9 @@ function sint32Of(int $num): Value
 
 /**
  * @api
- * @return Value<Number>
+ * @return Value<int>
  */
-function int64Of(Number $num): Value
+function int64Of(int $num): Value
 {
     return Value::int64($num);
 }
@@ -74,9 +74,9 @@ function uint64Of(Number $num): Value
 
 /**
  * @api
- * @return Value<Number>
+ * @return Value<int>
  */
-function sint64Of(Number $num): Value
+function sint64Of(int $num): Value
 {
     return Value::sint64($num);
 }
@@ -118,9 +118,9 @@ function fixed64Of(Number $num): Value
 
 /**
  * @api
- * @return Value<Number>
+ * @return Value<int>
  */
-function sfixed64Of(Number $num): Value
+function sfixed64Of(int $num): Value
 {
     return Value::sfixed64($num);
 }
diff --git a/tests/ScalarCardinalityTest.php b/tests/ScalarCardinalityTest.php
index cc87afe..025a3bf 100644
--- a/tests/ScalarCardinalityTest.php
+++ b/tests/ScalarCardinalityTest.php
@@ -112,15 +112,15 @@ public static function provideRoundTripCases(): iterable
                         'sint32' => Value::sint32(filter_var($value, FILTER_VALIDATE_INT)),
                         /** @phpstan-ignore argument.type */
                         'uint32' => Value::uint32(filter_var($value, FILTER_VALIDATE_INT)),
-                        'int64' => Value::int64(self::toNumber($value)),
+                        'int64' => Value::int64((int) $value),
                         'uint64' => Value::uint64(self::toNumber($value)),
-                        'sint64' => Value::sint64(self::toNumber($value)),
+                        'sint64' => Value::sint64((int) $value),
                         /** @phpstan-ignore argument.type */
                         'fixed32' => Value::fixed32(filter_var($value, FILTER_VALIDATE_INT)),
                         /** @phpstan-ignore argument.type */
                         'sfixed32' => Value::sfixed32(filter_var($value, FILTER_VALIDATE_INT)),
                         'fixed64' => Value::fixed64(self::toNumber($value)),
-                        'sfixed64' => Value::sfixed64(self::toNumber($value)),
+                        'sfixed64' => Value::sfixed64((int) $value),
                         default => throw new \UnexpectedValueException("Cannot handle type '{$type}'."),
                     },
                     $hex,
diff --git a/tests/testdata/reflection/all_in_one.php b/tests/testdata/reflection/all_in_one.php
index 0893dff..443904c 100644
--- a/tests/testdata/reflection/all_in_one.php
+++ b/tests/testdata/reflection/all_in_one.php
@@ -9,7 +9,7 @@
 final readonly class Nested
 {
     /**
-     * @param ?list<Number> $values
+     * @param ?list<int> $values
      */
     public function __construct(
         #[Reflection\Field(1, Reflection\Uint32T::T)]
@@ -76,7 +76,7 @@ public function __construct(
         #[Reflection\Field(1, Reflection\Int32T::T)]
         public ?int $aInt32 = null,
         #[Reflection\Field(2, Reflection\Int64T::T)]
-        public ?Number $aInt64 = null,
+        public ?int $aInt64 = null,
         #[Reflection\Field(3, Reflection\Uint32T::T)]
         public ?int $aUint32 = null,
         #[Reflection\Field(4, Reflection\Uint64T::T)]
@@ -84,7 +84,7 @@ public function __construct(
         #[Reflection\Field(5, Reflection\SInt32T::T)]
         public ?int $aSint32 = null,
         #[Reflection\Field(6, Reflection\SInt64T::T)]
-        public ?Number $aSint64 = null,
+        public ?int $aSint64 = null,
         #[Reflection\Field(7, Reflection\Fixed32T::T)]
         public ?int $aFixed32 = null,
         #[Reflection\Field(8, Reflection\Fixed64T::T)]
@@ -92,7 +92,7 @@ public function __construct(
         #[Reflection\Field(9, Reflection\SFixed32T::T)]
         public ?int $aSfixed32 = null,
         #[Reflection\Field(10, Reflection\SFixed64T::T)]
-        public ?Number $aSfixed64 = null,
+        public ?int $aSfixed64 = null,
         #[Reflection\Field(11, Reflection\FloatT::T)]
         public ?float $aFloat = null,
         #[Reflection\Field(12, Reflection\DoubleT::T)]