diff --git a/phpunit/code/class-exists-class-and-enum.php b/phpunit/code/class-exists-class-and-enum.php
new file mode 100644
index 00000000..234deb17
--- /dev/null
+++ b/phpunit/code/class-exists-class-and-enum.php
@@ -0,0 +1,22 @@
+<?php
+/**
+ * This file is part of TypePHP(AOT).
+ *
+ * @link     https://www.swoole.com/aot/
+ * @contact  service@swoole.com
+ */
+
+class Real
+{
+}
+
+enum Suit
+{
+    case Hearts;
+}
+
+function main(): void
+{
+    var_dump(class_exists('Real'));
+    var_dump(class_exists('Suit'));
+}
diff --git a/phpunit/code/class-exists-trait.php b/phpunit/code/class-exists-trait.php
new file mode 100644
index 00000000..9c5adb76
--- /dev/null
+++ b/phpunit/code/class-exists-trait.php
@@ -0,0 +1,16 @@
+<?php
+/**
+ * This file is part of TypePHP(AOT).
+ *
+ * @link     https://www.swoole.com/aot/
+ * @contact  service@swoole.com
+ */
+
+trait Helper
+{
+}
+
+function main(): void
+{
+    var_dump(class_exists('Helper'));
+}
diff --git a/phpunit/src/ClassExistsTraitFoldTest.php b/phpunit/src/ClassExistsTraitFoldTest.php
new file mode 100644
index 00000000..b511bb28
--- /dev/null
+++ b/phpunit/src/ClassExistsTraitFoldTest.php
@@ -0,0 +1,50 @@
+<?php
+/**
+ * This file is part of TypePHP(AOT).
+ *
+ * @link     https://www.swoole.com/aot/
+ * @contact  service@swoole.com
+ */
+
+namespace TypePhp\Tests;
+
+use PHPUnit\Framework\TestCase;
+use TypePhp\CompilerTest;
+
+/**
+ * @internal
+ * @coversNothing
+ */
+class ClassExistsTraitFoldTest extends TestCase
+{
+    public function testTraitNameFoldsToFalse(): void
+    {
+        $cpp = $this->compileToCpp('class-exists-trait.php');
+
+        // The trait is known at compile time, so the call is still folded -
+        // just to the answer PHP gives, which is false for a trait.
+        self::assertStringNotContainsString('php::fn::class_exists(', $cpp);
+        self::assertStringContainsString('= false;', $cpp);
+    }
+
+    public function testClassAndEnumNamesStillFoldToTrue(): void
+    {
+        $cpp = $this->compileToCpp('class-exists-class-and-enum.php');
+
+        self::assertStringNotContainsString('php::fn::class_exists(', $cpp);
+        self::assertStringNotContainsString('= false;', $cpp);
+    }
+
+    private function compileToCpp(string $file): string
+    {
+        global $translator;
+
+        $compiler = CompilerTest::create(TYPEPHP_ROOT_PATH);
+        $translator = $compiler;
+        $source = TYPEPHP_ROOT_PATH . '/phpunit/code/' . $file;
+        $compiler->addFiles([$source]);
+        $compiler->prepareFile($source);
+
+        return file_get_contents($compiler->convertFile($source));
+    }
+}
diff --git a/src/Optimizer/FuncCallOptimizer.php b/src/Optimizer/FuncCallOptimizer.php
index fe2ae690..423f0270 100644
--- a/src/Optimizer/FuncCallOptimizer.php
+++ b/src/Optimizer/FuncCallOptimizer.php
@@ -667,6 +667,11 @@ trait FuncCallOptimizer
         if (!$this->isScalarString($cn) || !$this->hasClass($cn->value)) {
             return false;
         }
+        // The class table also carries traits, but a trait is not a class to
+        // class_exists(): PHP answers false for it and true for an enum.
+        if ($this->getClassDef($cn->value)?->trait !== null) {
+            return 'false';
+        }
         return $this->isNativeObjectClass($cn->value) ? 'false' : 'true';
     }
 
diff --git a/tests/compiler/stdlib/class_exists.phpt b/tests/compiler/stdlib/class_exists.phpt
index bfab60a7..039466d1 100644
--- a/tests/compiler/stdlib/class_exists.phpt
+++ b/tests/compiler/stdlib/class_exists.phpt
@@ -16,6 +16,12 @@ function main() {
     var_dump(class_exists("NonexistentClass"));
     var_dump(class_exists("NonexistentClass", false));
 
+    // A trait is not a class. The answer must not depend on whether the name
+    // is a literal the compiler can resolve at compile time.
+    var_dump(class_exists("MyTrait"));
+    $traitName = "MyTrait";
+    var_dump(class_exists($traitName));
+
     // interface_exists
     var_dump(interface_exists("MyInterface"));
     var_dump(interface_exists("NonexistentInterface"));
@@ -38,6 +44,8 @@ bool(true)
 bool(true)
 bool(false)
 bool(false)
+bool(false)
+bool(false)
 bool(true)
 bool(false)
 bool(false)