diff --git a/lib/Nodes/Node.php b/lib/Nodes/Node.php
index b0ea4103..b85894bd 100644
--- a/lib/Nodes/Node.php
+++ b/lib/Nodes/Node.php
@@ -15,6 +15,7 @@
 use Doctrine\RST\Renderers\RenderedNode;
 
 use function implode;
+use function ltrim;
 use function strlen;
 use function substr;
 use function trim;
@@ -137,18 +138,25 @@ public function getValueString(): string
     protected function normalizeLines(array $lines): string
     {
         if ($lines !== []) {
-            $firstLine = $lines[0];
+            $indentLevel = null;
 
-            $k = 0;
+            // find the indentation by locating the line with the fewest preceding whitespace
+            foreach ($lines as $line) {
+                // skip empty lines
+                if (trim($line) === '') {
+                    continue;
+                }
 
-            for ($k = 0; $k < strlen($firstLine); $k++) {
-                if (trim($firstLine[$k]) !== '') {
-                    break;
+                $startingWhitespace = strlen($line) - strlen(ltrim($line));
+                if ($indentLevel !== null && $startingWhitespace > $indentLevel) {
+                    continue;
                 }
+
+                $indentLevel = $startingWhitespace;
             }
 
             foreach ($lines as &$line) {
-                $line = substr($line, $k);
+                $line = substr($line, $indentLevel);
             }
         }
 
diff --git a/tests/Functional/FunctionalTest.php b/tests/Functional/FunctionalTest.php
index 4c56fcc3..2cb36e99 100644
--- a/tests/Functional/FunctionalTest.php
+++ b/tests/Functional/FunctionalTest.php
@@ -32,6 +32,7 @@
 class FunctionalTest extends TestCase
 {
     private const RENDER_DOCUMENT_FILES = ['main-directive'];
+    private const SKIP_INDENTER_FILES   = ['code-block-diff'];
 
     protected function setUp(): void
     {
@@ -47,7 +48,8 @@ public function testFunctional(
         string $renderMethod,
         string $format,
         string $rst,
-        string $expected
+        string $expected,
+        bool $useIndenter = true
     ): void {
         $expectedLines = explode("\n", $expected);
         $firstLine     = $expectedLines[0];
@@ -68,7 +70,7 @@ public function testFunctional(
 
         $rendered = $document->$renderMethod();
 
-        if ($format === Format::HTML) {
+        if ($format === Format::HTML && $useIndenter) {
             $indenter = new Indenter();
             $rendered = $indenter->indent($rendered);
         }
@@ -133,7 +135,9 @@ public function getFunctionalTests(): array
                     ? 'renderDocument'
                     : 'render';
 
-                $tests[$basename . '_' . $format] = [$basename, $parser, $renderMethod, $format, $rst, trim($expected)];
+                $useIndenter = ! in_array($basename, self::SKIP_INDENTER_FILES, true);
+
+                $tests[$basename . '_' . $format] = [$basename, $parser, $renderMethod, $format, $rst, trim($expected), $useIndenter];
             }
         }
 
diff --git a/tests/Functional/tests/code-block-diff/code-block-diff.html b/tests/Functional/tests/code-block-diff/code-block-diff.html
new file mode 100644
index 00000000..d887b9b6
--- /dev/null
+++ b/tests/Functional/tests/code-block-diff/code-block-diff.html
@@ -0,0 +1,14 @@
+<pre><code class="diff">+ Added line
+- Removed line
+  Normal line
+- Removed line
++ Added line
+
+</code></pre>
+<pre><code class="diff">  Normal line
++ Added line
+- Removed line
+  Normal line
+- Removed line
++ Added line
+</code></pre>
diff --git a/tests/Functional/tests/code-block-diff/code-block-diff.rst b/tests/Functional/tests/code-block-diff/code-block-diff.rst
new file mode 100644
index 00000000..fce0f5f6
--- /dev/null
+++ b/tests/Functional/tests/code-block-diff/code-block-diff.rst
@@ -0,0 +1,18 @@
+
+.. code-block:: diff
+
+    + Added line
+    - Removed line
+      Normal line
+    - Removed line
+    + Added line
+
+
+.. code-block:: diff
+
+      Normal line
+    + Added line
+    - Removed line
+      Normal line
+    - Removed line
+    + Added line