diff --git a/core/modules/system/src/Tests/File/UnmanagedCopyTest.php b/core/modules/system/src/Tests/File/UnmanagedCopyTest.php
index f525c1d..0bb23c6 100644
--- a/core/modules/system/src/Tests/File/UnmanagedCopyTest.php
+++ b/core/modules/system/src/Tests/File/UnmanagedCopyTest.php
@@ -52,9 +52,13 @@ function testNormal() {
   function testNonExistent() {
     // Copy non-existent file
     $desired_filepath = $this->randomMachineName();
-    $this->assertFalse(file_exists($desired_filepath), "Randomly named file doesn't exists.");
-    $new_filepath = file_unmanaged_copy($desired_filepath, $this->randomMachineName());
-    $this->assertFalse($new_filepath, 'Copying a missing file fails.');
+    $this->assertFalse(file_exists($desired_filepath), "Randomly named file doesn't exist.");
+    try {
+      file_unmanaged_copy($desired_filepath, $this->randomMachineName());
+    }
+    catch (\Exception $e) {
+      $this->assertTrue($e->getMessage(), 'Copying a missing file fails.');
+    }
   }
 
   /**
diff --git a/core/modules/system/src/Tests/File/UnmanagedMoveTest.php b/core/modules/system/src/Tests/File/UnmanagedMoveTest.php
index ea39c54..9d33cda 100644
--- a/core/modules/system/src/Tests/File/UnmanagedMoveTest.php
+++ b/core/modules/system/src/Tests/File/UnmanagedMoveTest.php
@@ -52,8 +52,12 @@ function testNormal() {
    */
   function testMissing() {
     // Move non-existent file.
-    $new_filepath = file_unmanaged_move($this->randomMachineName(), $this->randomMachineName());
-    $this->assertFalse($new_filepath, 'Moving a missing file fails.');
+    try {
+      file_unmanaged_move($this->randomMachineName(), $this->randomMachineName());
+    }
+    catch (\Exception $e) {
+      $this->assertTrue($e->getMessage(), 'Moving a missing file fails.');
+    }
   }
 
   /**