diff --git a/independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/BeanArchives.java b/independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/BeanArchives.java
index 90695d500d94f..e54908eb06fee 100644
--- a/independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/BeanArchives.java
+++ b/independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/BeanArchives.java
@@ -279,6 +279,10 @@ static boolean index(Indexer indexer, String className, ClassLoader classLoader)
             // Ignore primitives and arrays
             return false;
         }
+        if (isInUnnamedPackage(className)) {
+            LOGGER.debugf("Class %s is defined in an unnamed package; skipping indexing", className);
+            return false;
+        }
         try (InputStream stream = classLoader
                 .getResourceAsStream(className.replace('.', '/') + ".class")) {
             if (stream != null) {
@@ -292,4 +296,8 @@ static boolean index(Indexer indexer, String className, ClassLoader classLoader)
         }
         return result;
     }
+
+    private static boolean isInUnnamedPackage(String className) {
+        return !className.contains(".");
+    }
 }
diff --git a/independent-projects/arc/processor/src/test/java/io/quarkus/arc/processor/BeanArchivesTest.java b/independent-projects/arc/processor/src/test/java/io/quarkus/arc/processor/BeanArchivesTest.java
new file mode 100644
index 0000000000000..bc33c4c92b5a9
--- /dev/null
+++ b/independent-projects/arc/processor/src/test/java/io/quarkus/arc/processor/BeanArchivesTest.java
@@ -0,0 +1,16 @@
+package io.quarkus.arc.processor;
+
+import org.jboss.jandex.Indexer;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class BeanArchivesTest {
+
+    @Test
+    public void testIndex() {
+        final Indexer indexer = new Indexer();
+        Assertions.assertFalse(BeanArchives.index(indexer, "String"));
+        Assertions.assertTrue(BeanArchives.index(indexer, String.class.getName()));
+    }
+
+}