diff --git a/src/CodeSnippets/FileSnippetProvider.php b/src/CodeSnippets/FileSnippetProvider.php
index 6fd5e30..b3656e6 100644
--- a/src/CodeSnippets/FileSnippetProvider.php
+++ b/src/CodeSnippets/FileSnippetProvider.php
@@ -21,7 +21,7 @@ public function numberOfLines(): int
         return $this->file->key() + 1;
     }
 
-    public function getLine(int $lineNumber = null): string
+    public function getLine(?int $lineNumber = null): string
     {
         if (is_null($lineNumber)) {
             return $this->getNextLine();
diff --git a/src/CodeSnippets/LaravelSerializableClosureSnippetProvider.php b/src/CodeSnippets/LaravelSerializableClosureSnippetProvider.php
index 1dc9351..0cd41c2 100644
--- a/src/CodeSnippets/LaravelSerializableClosureSnippetProvider.php
+++ b/src/CodeSnippets/LaravelSerializableClosureSnippetProvider.php
@@ -22,7 +22,7 @@ public function numberOfLines(): int
         return count($this->lines);
     }
 
-    public function getLine(int $lineNumber = null): string
+    public function getLine(?int $lineNumber = null): string
     {
         if (is_null($lineNumber)) {
             return $this->getNextLine();
diff --git a/src/CodeSnippets/NullSnippetProvider.php b/src/CodeSnippets/NullSnippetProvider.php
index 9fda38f..220029e 100644
--- a/src/CodeSnippets/NullSnippetProvider.php
+++ b/src/CodeSnippets/NullSnippetProvider.php
@@ -9,7 +9,7 @@ public function numberOfLines(): int
         return 1;
     }
 
-    public function getLine(int $lineNumber = null): string
+    public function getLine(?int $lineNumber = null): string
     {
         return $this->getNextLine();
     }
diff --git a/src/CodeSnippets/SnippetProvider.php b/src/CodeSnippets/SnippetProvider.php
index bed22ba..7064b92 100644
--- a/src/CodeSnippets/SnippetProvider.php
+++ b/src/CodeSnippets/SnippetProvider.php
@@ -6,7 +6,7 @@ interface SnippetProvider
 {
     public function numberOfLines(): int;
 
-    public function getLine(int $lineNumber = null): string;
+    public function getLine(?int $lineNumber = null): string;
 
     public function getNextLine(): string;
 }