diff --git a/doc/internals.rst b/doc/internals.rst
index 97661411d..07ff85534 100644
--- a/doc/internals.rst
+++ b/doc/internals.rst
@@ -124,7 +124,7 @@ using)::
     /* Hello {{ name }} */
     class __TwigTemplate_1121b6f109fe93ebe8c6e22e3712bceb extends Template
     {
-        protected function doDisplay(array $context, array $blocks = [])
+        protected function doDisplay(array $context, array $blocks = []): iterable
         {
             $macros = $this->macros;
             // line 1
diff --git a/src/Node/BlockNode.php b/src/Node/BlockNode.php
index d2cfc3bd8..2ee74a8d2 100644
--- a/src/Node/BlockNode.php
+++ b/src/Node/BlockNode.php
@@ -32,7 +32,10 @@ class BlockNode extends Node
     {
         $compiler
             ->addDebugInfo($this)
-            ->write(\sprintf("public function block_%s(\$context, array \$blocks = [])\n", $this->getAttribute('name')), "{\n")
+            ->write("/**\n")
+            ->write(" * @return iterable<string>\n")
+            ->write(" */\n")
+            ->write(\sprintf("public function block_%s(array \$context, array \$blocks = []): iterable\n", $this->getAttribute('name')), "{\n")
             ->indent()
             ->write("\$macros = \$this->macros;\n")
         ;
diff --git a/src/Node/ModuleNode.php b/src/Node/ModuleNode.php
index deb05a16f..264a0e67f 100644
--- a/src/Node/ModuleNode.php
+++ b/src/Node/ModuleNode.php
@@ -318,7 +318,7 @@ final class ModuleNode extends Node
     protected function compileDisplay(Compiler $compiler)
     {
         $compiler
-            ->write("protected function doDisplay(array \$context, array \$blocks = [])\n", "{\n")
+            ->write("protected function doDisplay(array \$context, array \$blocks = []): iterable\n", "{\n")
             ->indent()
             ->write("\$macros = \$this->macros;\n")
             ->subcompile($this->getNode('display_start'))
diff --git a/src/Template.php b/src/Template.php
index 653462db6..ec9db9bf6 100644
--- a/src/Template.php
+++ b/src/Template.php
@@ -74,7 +74,7 @@ abstract class Template
      *
      * @return self|TemplateWrapper|false The parent template or false if there is no parent
      */
-    public function getParent(array $context)
+    public function getParent(array $context): self|TemplateWrapper|false
     {
         if (null !== $this->parent) {
             return $this->parent;
@@ -122,7 +122,7 @@ abstract class Template
      * @param array  $context The context
      * @param array  $blocks  The current set of blocks
      */
-    public function displayParentBlock($name, array $context, array $blocks = [])
+    public function displayParentBlock($name, array $context, array $blocks = []): void
     {
         foreach ($this->yieldParentBlock($name, $context, $blocks) as $data) {
             echo $data;
@@ -140,7 +140,7 @@ abstract class Template
      * @param array  $blocks    The current set of blocks
      * @param bool   $useBlocks Whether to use the current set of blocks
      */
-    public function displayBlock($name, array $context, array $blocks = [], $useBlocks = true, ?self $templateContext = null)
+    public function displayBlock($name, array $context, array $blocks = [], $useBlocks = true, ?self $templateContext = null): void
     {
         foreach ($this->yieldBlock($name, $context, $blocks, $useBlocks, $templateContext) as $data) {
             echo $data;
@@ -159,7 +159,7 @@ abstract class Template
      *
      * @return string The rendered block
      */
-    public function renderParentBlock($name, array $context, array $blocks = [])
+    public function renderParentBlock($name, array $context, array $blocks = []): string
     {
         if (!$this->useYield) {
             if ($this->env->isDebug()) {
@@ -193,7 +193,7 @@ abstract class Template
      *
      * @return string The rendered block
      */
-    public function renderBlock($name, array $context, array $blocks = [], $useBlocks = true)
+    public function renderBlock($name, array $context, array $blocks = [], $useBlocks = true): string
     {
         if (!$this->useYield) {
             $level = ob_get_level();
@@ -235,7 +235,7 @@ abstract class Template
      *
      * @return bool true if the block exists, false otherwise
      */
-    public function hasBlock($name, array $context, array $blocks = [])
+    public function hasBlock($name, array $context, array $blocks = []): bool
     {
         if (isset($blocks[$name])) {
             return $blocks[$name][0] instanceof self;
@@ -261,9 +261,9 @@ abstract class Template
      * @param array $context The context
      * @param array $blocks  The current set of blocks
      *
-     * @return array An array of block names
+     * @return array<string> An array of block names
      */
-    public function getBlockNames(array $context, array $blocks = [])
+    public function getBlockNames(array $context, array $blocks = []): array
     {
         $names = array_merge(array_keys($blocks), array_keys($this->blocks));
 
@@ -276,10 +276,8 @@ abstract class Template
 
     /**
      * @param string|TemplateWrapper|array<string|TemplateWrapper> $template
-     *
-     * @return self|TemplateWrapper
      */
-    protected function loadTemplate($template, $templateName = null, $line = null, $index = null)
+    protected function loadTemplate($template, $templateName = null, $line = null, $index = null): self|TemplateWrapper
     {
         try {
             if (\is_array($template)) {
@@ -327,10 +325,8 @@ abstract class Template
 
     /**
      * @internal
-     *
-     * @return self
      */
-    public function unwrap()
+    public function unwrap(): self
     {
         return $this;
     }
@@ -343,7 +339,7 @@ abstract class Template
      *
      * @return array An array of blocks
      */
-    public function getBlocks()
+    public function getBlocks(): array
     {
         return $this->blocks;
     }
@@ -418,7 +414,7 @@ abstract class Template
     /**
      * @return iterable<string>
      */
-    public function yieldBlock($name, array $context, array $blocks = [], $useBlocks = true, ?self $templateContext = null)
+    public function yieldBlock($name, array $context, array $blocks = [], $useBlocks = true, ?self $templateContext = null): iterable
     {
         if ($useBlocks && isset($blocks[$name])) {
             $template = $blocks[$name][0];
@@ -478,7 +474,7 @@ abstract class Template
      *
      * @return iterable<string>
      */
-    public function yieldParentBlock($name, array $context, array $blocks = [])
+    public function yieldParentBlock($name, array $context, array $blocks = []): iterable
     {
         if (isset($this->traits[$name])) {
             yield from $this->traits[$name][0]->yieldBlock($name, $context, $blocks, false);
@@ -494,6 +490,8 @@ abstract class Template
      *
      * @param array $context An array of parameters to pass to the template
      * @param array $blocks  An array of blocks to pass to the template
+
+     * @return iterable<string>
      */
-    abstract protected function doDisplay(array $context, array $blocks = []);
+    abstract protected function doDisplay(array $context, array $blocks = []): iterable;
 }
diff --git a/tests/Node/BlockTest.php b/tests/Node/BlockTest.php
index 0938e74a1..02de54b4a 100644
--- a/tests/Node/BlockTest.php
+++ b/tests/Node/BlockTest.php
@@ -33,7 +33,10 @@ class BlockTest extends NodeTestCase
         $tests = [];
         $tests[] = [new BlockNode('foo', new TextNode('foo', 1), 1), <<<EOF
 // line 1
-public function block_foo(\$context, array \$blocks = [])
+/**
+ * @return iterable<string>
+ */
+public function block_foo(array \$context, array \$blocks = []): iterable
 {
     \$macros = \$this->macros;
     yield "foo";
diff --git a/tests/Node/ModuleTest.php b/tests/Node/ModuleTest.php
index f3081dff9..0b7dd5ddb 100644
--- a/tests/Node/ModuleTest.php
+++ b/tests/Node/ModuleTest.php
@@ -98,7 +98,7 @@ class __TwigTemplate_%x extends Template
         ];
     }
 
-    protected function doDisplay(array \$context, array \$blocks = [])
+    protected function doDisplay(array \$context, array \$blocks = []): iterable
     {
         \$macros = \$this->macros;
         // line 1
@@ -178,7 +178,7 @@ class __TwigTemplate_%x extends Template
         return "layout.twig";
     }
 
-    protected function doDisplay(array \$context, array \$blocks = [])
+    protected function doDisplay(array \$context, array \$blocks = []): iterable
     {
         \$macros = \$this->macros;
         // line 2
@@ -273,7 +273,7 @@ class __TwigTemplate_%x extends Template
         return \$this->loadTemplate(((true) ? ("foo") : ("foo")), "foo.twig", 2);
     }
 
-    protected function doDisplay(array \$context, array \$blocks = [])
+    protected function doDisplay(array \$context, array \$blocks = []): iterable
     {
         \$macros = \$this->macros;
         // line 4
diff --git a/tests/TemplateTest.php b/tests/TemplateTest.php
index 884226e0a..2756c5774 100644
--- a/tests/TemplateTest.php
+++ b/tests/TemplateTest.php
@@ -464,7 +464,7 @@ class TemplateForTest extends Template
         return false;
     }
 
-    protected function doDisplay(array $context, array $blocks = [])
+    protected function doDisplay(array $context, array $blocks = []): iterable
     {
     }