diff --git a/CHANGELOG.md b/CHANGELOG.md
index e3257b06..465e8fd1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ Latest
 * [#241](https://github.com/cleverage/process-bundle/issues/241) Fix CsvWriterTask: a non-array input throws the documented `\UnexpectedValueException` instead of a `TypeError` when `headers` is `null`, and the CSV tasks release their file on `finalize()` so that the task can be executed again. Update documentation, add tests.
 * [#240](https://github.com/cleverage/process-bundle/issues/240) Fix FileMoverTask: with `autoincrement`, the suffix was computed on the whole path (a dot in a directory name was taken as the extension, making the move fail for a file without extension) and an existing numeric suffix of the file name was replaced (`report-2024.csv` became `report-1.csv`). The suffix is now appended to the file name only (`report-2024-1.csv`, `file-1`, `.env-1`). Update documentation, add tests.
 * [#243](https://github.com/cleverage/process-bundle/issues/243) Fix RecursivePropertySetterTransformer: a `\stdClass` item without the property was replaced by a copy in the output, so the input object was not modified; the property is now added to the item itself. Update documentation, add tests.
+* [#242](https://github.com/cleverage/process-bundle/issues/242) Fix InputFileReaderTask: an input that is not a non-empty string (e.g. `null`) throws an explicit `\UnexpectedValueException` (`No file path given as input`) instead of a PHP warning followed by a `TypeError`. Update documentation, add tests.
 
 v5.1
 -----
diff --git a/docs/reference/tasks/input_file_reader_task.md b/docs/reference/tasks/input_file_reader_task.md
index 39e5e06b..ac9413f9 100644
--- a/docs/reference/tasks/input_file_reader_task.md
+++ b/docs/reference/tasks/input_file_reader_task.md
@@ -12,8 +12,8 @@ Task reference
 Accepted inputs
 ---------------
 
-`string`: path of the file to read. An `\UnexpectedValueException` is thrown if the file does not exist or is not
-readable.
+`string`: path of the file to read. An `\UnexpectedValueException` is thrown if the input is not a non-empty string
+(e.g. `null`, `''`), or if the file does not exist or is not readable.
 
 Possible outputs
 ----------------
diff --git a/src/Task/File/InputFileReaderTask.php b/src/Task/File/InputFileReaderTask.php
index b2b36178..9d002370 100644
--- a/src/Task/File/InputFileReaderTask.php
+++ b/src/Task/File/InputFileReaderTask.php
@@ -21,6 +21,13 @@
  */
 class InputFileReaderTask extends FileReaderTask
 {
+    #[\Override]
+    public function initialize(ProcessState $state): void
+    {
+        // Only validate the options: the file path comes from the input
+        parent::getOptions($state);
+    }
+
     /**
      * @return array<string, mixed>
      */
@@ -28,9 +35,11 @@ class InputFileReaderTask extends FileReaderTask
     protected function getOptions(ProcessState $state): array
     {
         $options = parent::getOptions($state);
-        if (null !== $state->getInput()) {
-            $options['filename'] = $state->getInput();
+        $filename = $state->getInput();
+        if (!\is_string($filename) || '' === $filename) {
+            throw new \UnexpectedValueException('No file path given as input');
         }
+        $options['filename'] = $filename;
 
         return $options;
     }
diff --git a/tests/Task/File/InputFileReaderTaskTest.php b/tests/Task/File/InputFileReaderTaskTest.php
index 96551daf..bcbd10da 100644
--- a/tests/Task/File/InputFileReaderTaskTest.php
+++ b/tests/Task/File/InputFileReaderTaskTest.php
@@ -107,6 +107,29 @@ public function testThrowsWhenInputFileIsNotReadable(): void
         $this->read($task, $state, $filename);
     }
 
+    /**
+     * @return iterable<string, array{mixed}>
+     */
+    public static function invalidInputProvider(): iterable
+    {
+        yield 'null' => [null];
+        yield 'empty string' => [''];
+        yield 'array' => [['a.txt']];
+    }
+
+    #[\PHPUnit\Framework\Attributes\DataProvider('invalidInputProvider')]
+    public function testThrowsWhenNoFilePathIsGivenAsInput(mixed $input): void
+    {
+        $task = new InputFileReaderTask();
+        $state = $this->createState([]);
+        $task->initialize($state);
+
+        $this->expectException(\UnexpectedValueException::class);
+        $this->expectExceptionMessage('No file path given as input');
+
+        $this->read($task, $state, $input);
+    }
+
     public function testRejectsFilenameOption(): void
     {
         $task = new InputFileReaderTask();