diff --git a/src/BigDecimal.php b/src/BigDecimal.php
index b84f505..7824650 100644
--- a/src/BigDecimal.php
+++ b/src/BigDecimal.php
@@ -752,6 +752,40 @@ public function __toString() : string
         return \substr($value, 0, -$this->scale) . '.' . \substr($value, -$this->scale);
     }
 
+    /**
+     * This method is required for serializing the object and SHOULD NOT be accessed directly.
+     *
+     * @internal
+     *
+     * @return array{value: string, scale: int}
+     */
+    public function __serialize(): array
+    {
+        return ['value' => $this->value, 'scale' => $this->scale];
+    }
+
+    /**
+     * This method is only here to allow unserializing the object and cannot be accessed directly.
+     *
+     * @internal
+     * @psalm-suppress RedundantPropertyInitializationCheck
+     *
+     * @param array{value: string, scale: int} $data
+     *
+     * @return void
+     *
+     * @throws \LogicException
+     */
+    public function __unserialize(array $data): void
+    {
+        if (isset($this->value)) {
+            throw new \LogicException('__unserialize() is an internal function, it must not be called directly.');
+        }
+
+        $this->value = $data['value'];
+        $this->scale = $data['scale'];
+    }
+
     /**
      * This method is required by interface Serializable and SHOULD NOT be accessed directly.
      *
diff --git a/src/BigInteger.php b/src/BigInteger.php
index 0dcc8f3..f213fbe 100644
--- a/src/BigInteger.php
+++ b/src/BigInteger.php
@@ -1116,6 +1116,39 @@ public function __toString() : string
         return $this->value;
     }
 
+    /**
+     * This method is required for serializing the object and SHOULD NOT be accessed directly.
+     *
+     * @internal
+     *
+     * @return array{value: string}
+     */
+    public function __serialize(): array
+    {
+        return ['value' => $this->value];
+    }
+
+    /**
+     * This method is only here to allow unserializing the object and cannot be accessed directly.
+     *
+     * @internal
+     * @psalm-suppress RedundantPropertyInitializationCheck
+     *
+     * @param array{value: string} $data
+     *
+     * @return void
+     *
+     * @throws \LogicException
+     */
+    public function __unserialize(array $data): void
+    {
+        if (isset($this->value)) {
+            throw new \LogicException('__unserialize() is an internal function, it must not be called directly.');
+        }
+
+        $this->value = $data['value'];
+    }
+
     /**
      * This method is required by interface Serializable and SHOULD NOT be accessed directly.
      *
diff --git a/src/BigRational.php b/src/BigRational.php
index 7fbabd7..8446ee2 100644
--- a/src/BigRational.php
+++ b/src/BigRational.php
@@ -451,6 +451,40 @@ public function __toString() : string
         return $this->numerator . '/' . $this->denominator;
     }
 
+    /**
+     * This method is required for serializing the object and SHOULD NOT be accessed directly.
+     *
+     * @internal
+     *
+     * @return array{numerator: \Brick\Math\BigInteger, denominator: \Brick\Math\BigInteger}
+     */
+    public function __serialize(): array
+    {
+        return ['numerator' => $this->numerator, 'denominator' => $this->denominator];
+    }
+
+    /**
+     * This method is only here to allow unserializing the object and cannot be accessed directly.
+     *
+     * @internal
+     * @psalm-suppress RedundantPropertyInitializationCheck
+     *
+     * @param array{numerator: \Brick\Math\BigInteger, denominator: \Brick\Math\BigInteger} $data
+     *
+     * @return void
+     *
+     * @throws \LogicException
+     */
+    public function __unserialize(array $data): void
+    {
+        if (isset($this->numerator)) {
+            throw new \LogicException('__unserialize() is an internal function, it must not be called directly.');
+        }
+
+        $this->numerator = $data['numerator'];
+        $this->denominator = $data['denominator'];
+    }
+
     /**
      * This method is required by interface Serializable and SHOULD NOT be accessed directly.
      *