diff --git a/tools/aconfig/src/codegen.rs b/tools/aconfig/src/codegen.rs
index fe52c8d..b7fb08f 100644
--- a/tools/aconfig/src/codegen.rs
+++ b/tools/aconfig/src/codegen.rs
@@ -32,6 +32,9 @@
 }
 
 pub fn is_valid_package_ident(s: &str) -> bool {
+    if !s.contains('.') {
+        return false;
+    }
     s.split('.').all(is_valid_name_ident)
 }
 
@@ -61,11 +64,12 @@
 
     #[test]
     fn test_is_valid_package_ident() {
-        assert!(is_valid_package_ident("foo"));
-        assert!(is_valid_package_ident("foo_bar_123"));
         assert!(is_valid_package_ident("foo.bar"));
+        assert!(is_valid_package_ident("foo.bar_baz"));
         assert!(is_valid_package_ident("foo.bar.a123"));
 
+        assert!(!is_valid_package_ident("foo_bar_123"));
+        assert!(!is_valid_package_ident("foo"));
         assert!(!is_valid_package_ident("foo._bar"));
         assert!(!is_valid_package_ident(""));
         assert!(!is_valid_package_ident("123_foo"));
@@ -75,6 +79,7 @@
         assert!(!is_valid_package_ident(".foo.bar"));
         assert!(!is_valid_package_ident("foo.bar."));
         assert!(!is_valid_package_ident("."));
+        assert!(!is_valid_package_ident(".."));
         assert!(!is_valid_package_ident("foo..bar"));
         assert!(!is_valid_package_ident("foo.__bar"));
     }
diff --git a/tools/aconfig/src/protos.rs b/tools/aconfig/src/protos.rs
index 4d824f2..17019be 100644
--- a/tools/aconfig/src/protos.rs
+++ b/tools/aconfig/src/protos.rs
@@ -549,7 +549,7 @@
         // bad input: parsed_flag not sorted by package
         let text_proto = r#"
 parsed_flag {
-    package: "bbb"
+    package: "bbb.bbb"
     name: "first"
     namespace: "first_ns"
     description: "This is the description of the first flag."
@@ -562,7 +562,7 @@
     }
 }
 parsed_flag {
-    package: "aaa"
+    package: "aaa.aaa"
     name: "second"
     namespace: "second_ns"
     description: "This is the description of the second flag."
@@ -578,7 +578,7 @@
         let error = try_from_binary_proto_from_text_proto(text_proto).unwrap_err();
         assert_eq!(
             format!("{:?}", error),
-            "bad parsed flags: not sorted: bbb.first comes before aaa.second"
+            "bad parsed flags: not sorted: bbb.bbb.first comes before aaa.aaa.second"
         );
 
         // bad input: parsed_flag not sorted by name