diff --git a/src/CodegenFile.php b/src/CodegenFile.php
index 46816287..868bf8d4 100644
--- a/src/CodegenFile.php
+++ b/src/CodegenFile.php
@@ -16,6 +16,13 @@ enum CodegenFileResult: int {
   CREATE = 2;
 }
 
+enum CodegenFileType: int {
+  PHP = 0;
+  HACK_DECL = 1;
+  HACK_PARTIAL = 2;
+  HACK_STRICT = 3;
+}
+
 /**
  * File of generated code. The file is composed by classes.
  * The file will be signed, either as autogenerated or partially generated,
@@ -23,7 +30,7 @@ enum CodegenFileResult: int {
  */
 final class CodegenFile {
 
-  private bool $isStrict = false;
+  private CodegenFileType $fileType = CodegenFileType::HACK_PARTIAL;
   private ?string $docBlock;
   private string $fileName;
   private string $relativeFileName;
@@ -175,10 +182,20 @@ public function rekeyManualSection(string $old_key, string $new_key): this {
   }
 
   /**
-   * Whether the generated file will be Hack strict mode
+   * Whether the generated file will be Hack strict mode or partial mode.
+   * For more flexibility, use setFileType.
    */
   public function setIsStrict(bool $value): this {
-    $this->isStrict = $value;
+    if ($value) {
+      $this->setFileType(CodegenFileType::HACK_STRICT);
+    } else {
+      $this->setFileType(CodegenFileType::HACK_PARTIAL);
+    }
+    return $this;
+  }
+
+  public function setFileType(CodegenFileType $type): this {
+    $this->fileType = $type;
     return $this;
   }
 
@@ -202,14 +219,23 @@ public function getFormatter(): ?ICodegenFormatter {
   }
 
 
+  private function getFileTypeDeclaration(): string {
+    switch($this->fileType) {
+      case CodegenFileType::PHP:
+        return '<?php';
+      case CodegenFileType::HACK_DECL:
+        return '<?hh // decl';
+      case CodegenFileType::HACK_PARTIAL:
+        return '<?hh';
+      case CodegenFileType::HACK_STRICT:
+        return '<?hh // strict';
+    }
+  }
+
   public function render(): string {
     $builder = hack_builder();
 
-    $first_line = '<?hh';
-    if ($this->isStrict) {
-      $first_line .= ' // strict';
-    }
-    $builder->addLine($first_line);
+    $builder->addLine($this->getFileTypeDeclaration());
     $header = $this->config->getFileHeader();
     if ($header) {
       foreach ($header as $line) {
diff --git a/test/CodegenFileTestCase.codegen b/test/CodegenFileTestCase.codegen
index 58dea2c4..ebf11d22 100644
--- a/test/CodegenFileTestCase.codegen
+++ b/test/CodegenFileTestCase.codegen
@@ -83,6 +83,18 @@ class PartiallyGenerated {
 class PartiallyGeneratedLoader {
 }
 
+!@#$%codegentest:testPhpFile
+<?php
+// Codegen Tests
+/**
+ * This file is generated. Do not modify it manually!
+ *
+ * @-generated SignedSource<<75ccd5361b4a4337b9ded246a44f3b4c>>
+ */
+
+class Foo {
+}
+
 !@#$%codegentest:testSaveAutogenerated
 <?hh
 // Codegen Tests
@@ -122,3 +134,15 @@ class Demo {
   }
 }
 
+!@#$%codegentest:testStrictFile
+<?hh // strict
+// Codegen Tests
+/**
+ * This file is generated. Do not modify it manually!
+ *
+ * @-generated SignedSource<<5c0182dcd097a22f08d4dfbcc555c52c>>
+ */
+
+class Foo {
+}
+
diff --git a/test/CodegenFileTestCase.php b/test/CodegenFileTestCase.php
index fdb582c1..873741b6 100644
--- a/test/CodegenFileTestCase.php
+++ b/test/CodegenFileTestCase.php
@@ -245,4 +245,22 @@ public function testNamespace() {
     self::assertUnchanged($code);
   }
 
+  public function testStrictFile() {
+    $code = test_codegen_file('no_file')
+      ->setIsStrict(true)
+      ->addClass(codegen_class('Foo'))
+      ->render();
+
+    self::assertUnchanged($code);
+  }
+
+  public function testPhpFile() {
+    $code = test_codegen_file('no_file')
+      ->setFileType(CodegenFileType::PHP)
+      ->addClass(codegen_class('Foo'))
+      ->render();
+
+    self::assertUnchanged($code);
+  }
+
 }