diff --git a/library/Requests/Exception/InvalidArgument.php b/library/Requests/Exception/InvalidArgument.php
new file mode 100644
index 000000000..7f43d595f
--- /dev/null
+++ b/library/Requests/Exception/InvalidArgument.php
@@ -0,0 +1,8 @@
+<?php
+
+/**
+ * Exception for an invalid argument passed
+ *
+ * @package Requests
+ */
+class Requests_Exception_InvalidArgument extends InvalidArgumentException {}
diff --git a/library/Requests/Transport/cURL.php b/library/Requests/Transport/cURL.php
index 4cd10866a..d7b51101a 100644
--- a/library/Requests/Transport/cURL.php
+++ b/library/Requests/Transport/cURL.php
@@ -130,6 +130,25 @@ public function __destruct() {
 	 * @return string Raw HTTP result
 	 */
 	public function request($url, $headers = array(), $data = array(), $options = array()) {
+		if (is_array($data) === false && is_string($data) === false) {
+			if ($data === null) {
+				$data = '';
+			} elseif (is_int($data) || is_float($data)) {
+				$data = (string) $data;
+			} else {
+				throw new Requests_Exception_InvalidArgument(
+					sprintf(
+						'%s: Argument #%d (%s) must be of type %s, %s given',
+						__METHOD__,
+						3,
+						'$data',
+						'array|string',
+						gettype($data)
+					)
+				);
+			}
+		}
+
 		$this->hooks = $options['hooks'];
 
 		$this->setup_handle($url, $headers, $data, $options);
diff --git a/library/Requests/Transport/fsockopen.php b/library/Requests/Transport/fsockopen.php
index 34b65d4a6..c6ff4ad33 100644
--- a/library/Requests/Transport/fsockopen.php
+++ b/library/Requests/Transport/fsockopen.php
@@ -56,6 +56,25 @@ class Requests_Transport_fsockopen implements Requests_Transport {
 	 * @return string Raw HTTP result
 	 */
 	public function request($url, $headers = array(), $data = array(), $options = array()) {
+		if (is_array($data) === false && is_string($data) === false) {
+			if ($data === null) {
+				$data = '';
+			} elseif (is_int($data) || is_float($data)) {
+				$data = (string) $data;
+			} else {
+				throw new Requests_Exception_InvalidArgument(
+					sprintf(
+						'%s: Argument #%d (%s) must be of type %s, %s given',
+						__METHOD__,
+						3,
+						'$data',
+						'array|string',
+						gettype($data)
+					)
+				);
+			}
+		}
+
 		$options['hooks']->dispatch('fsockopen.before_request');
 
 		$url_parts = parse_url($url);
diff --git a/tests/Transport/Base.php b/tests/Transport/Base.php
index 066c5ff5a..68b5336c7 100644
--- a/tests/Transport/Base.php
+++ b/tests/Transport/Base.php
@@ -167,6 +167,77 @@ public function testEmptyPOST() {
 		}
 	}
 
+	/**
+	 * Test that when a $data parameter of an incorrect type gets passed, it gets handled correctly.
+	 *
+	 * Only string/array are officially supported as accepted data types, but null, integers and floats
+	 * will also be handled (cast to string).
+	 *
+	 * Original test passing `null` was added in response to issue #248.
+	 * The test was expanded to additional data types in response to changes in PHP 8.1.
+	 *
+	 * @dataProvider dataIncorrectDataTypeAccepted
+	 *
+	 * @param mixed  $data     Input to be used as the $data parameter.
+	 * @param string $expected Expected content-length header.
+	 *
+	 * @return void
+	 */
+	public function testIncorrectDataTypeAcceptedPOST($data, $expected) {
+		$request = Requests::post(httpbin('/post'), array(), $data, $this->getOptions());
+		$this->assertIsObject($request, 'POST request did not return an object');
+		$this->assertObjectHasAttribute('status_code', $request, 'POST request object does not have a "status_code" property');
+		$this->assertSame(200, $request->status_code, 'POST request status code is not 200');
+
+		$this->assertObjectHasAttribute('body', $request, 'POST request object does not have a "body" property');
+		$result = json_decode($request->body, true);
+
+		$this->assertIsArray($result, 'Json decoded POST request body is not an array');
+		$this->assertArrayHasKey('data', $result, 'Json decoded POST request body does not contain array key "data"');
+		$this->assertSame($expected, $result['data'],'Json decoded POST request body "data" key did not match expected contents' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array
+	 */
+	public function dataIncorrectDataTypeAccepted() {
+		return array(
+			'null'    => array(null, ''),
+			'integer' => array(12345, '12345'),
+			'float'   => array(12.345, '12.345'),
+		);
+	}
+
+	/**
+	 * Test that when a $data parameter of an unhandled incorrect type gets passed, an exception gets thrown.
+	 *
+	 * @dataProvider dataIncorrectDataTypeException
+	 *
+	 * @param mixed $data Input to be used as the $data parameter.
+	 *
+	 * @return void
+	 */
+	public function testIncorrectDataTypeExceptionPOST($data) {
+		$this->expectException('Requests_Exception_InvalidArgument');
+		$this->expectExceptionMessage('Argument #3 ($data) must be of type array|string');
+
+		$request = Requests::post(httpbin('/post'), array(), $data, $this->getOptions());
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array
+	 */
+	public function dataIncorrectDataTypeException() {
+		return array(
+			'boolean' => array(true),
+			'object'  => array(new stdClass()),
+		);
+	}
+
 	public function testFormPost() {
 		$data    = 'test=true&test2=test';
 		$request = Requests::post(httpbin('/post'), array(), $data, $this->getOptions());