diff --git a/src/core/ComposableElement.php b/src/core/ComposableElement.php
index ca3c4fee..073e6511 100644
--- a/src/core/ComposableElement.php
+++ b/src/core/ComposableElement.php
@@ -522,6 +522,17 @@ final protected function validateAttributeValue<T>(
         if (enum_exists($class) && $class::isValid($val)) {
           break;
         }
+        // Things that are a valid array key without any coercion
+        if ($class === 'HH\arraykey') {
+          if (is_int($val) || is_string($val)) {
+            break;
+          }
+        }
+        if ($class === 'HH\num') {
+          if (is_int($val) || is_float($val)) {
+            break;
+          }
+        }
         throw new XHPInvalidAttributeException(
           $this, $class, $attr, $val
         );
diff --git a/tests/AttributesTest.php b/tests/AttributesTest.php
index 1bdba0d1..ddf493d3 100644
--- a/tests/AttributesTest.php
+++ b/tests/AttributesTest.php
@@ -12,7 +12,9 @@ class :test:attribute-types extends :x:element {
     enum {'foo', 'bar'} myenum,
     float myfloat,
     Vector<string> myvector,
-    Map<string, string> mymap;
+    Map<string, string> mymap,
+    arraykey myarraykey,
+    num mynum;
 
   protected function render(): XHPRoot {
     return <div />;
@@ -69,6 +71,36 @@ public function testValidTypes(): void {
     $this->assertEquals('<div></div>', $x->toString());
   }
 
+  public function testValidArrayKeys(): void {
+    $x = <test:attribute-types myarraykey="foo" />;
+    $this->assertSame('<div></div>', $x->toString());
+    $x = <test:attribute-types myarraykey={123} />;
+    $this->assertSame('<div></div>', $x->toString());
+  }
+
+  /**
+   * @expectedException XHPInvalidAttributeException
+   */
+  public function testInvalidArrayKeys(): void {
+    $x = <test:attribute-types myarraykey={1.23} />;
+    $x->toString();
+  }
+
+  public function testValidNum(): void {
+    $x = <test:attribute-types mynum={123} />;
+    $this->assertSame('<div></div>', $x->toString());
+    $x = <test:attribute-types mynum={1.23} />;
+    $this->assertSame('<div></div>', $x->toString());
+  }
+
+  /**
+   * @expectedException XHPInvalidAttributeException
+   */
+  public function testInvalidNum(): void {
+    $x = <test:attribute-types mynum="123" />;
+    $x->toString();
+  }
+
   public function testNoAttributes(): void {
     $this->assertEquals('<div></div>', <test:attribute-types />);
   }