diff --git a/README.md b/README.md
index 82fa7a5..a63801c 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,14 @@ Also, you can combine them (very handy for blog posts and tweets):
 vendor/bin/lines measure src --short --json
 ```
 
+<br>
+
+Are you looking for top 10 longest files?
+
+```bash
+vendor/bin/lines measure src --longest
+```
+
 ## The Measured Items
 
 For the text output, you'll get data like these:
diff --git a/src/Measurements.php b/src/Measurements.php
index 5bd0b3b..556f8b0 100644
--- a/src/Measurements.php
+++ b/src/Measurements.php
@@ -58,7 +58,7 @@ public function addFile(string $filename): void
         $this->directoryNames[] = dirname($filename);
 
         $relativeFilePath = str_replace(getcwd() . '/', '', $filename);
-        $this->filesToSize[$relativeFilePath] = substr_count(file_get_contents($filename), "\n") + 1;
+        $this->filesToSize[$relativeFilePath] = substr_count((string) file_get_contents($filename), "\n") + 1;
 
         ++$this->fileCount;
     }