diff --git a/framework/src/android/net/apf/ApfCapabilities.java b/framework/src/android/net/apf/ApfCapabilities.java
index 6b18629..f92cdbb 100644
--- a/framework/src/android/net/apf/ApfCapabilities.java
+++ b/framework/src/android/net/apf/ApfCapabilities.java
@@ -106,6 +106,8 @@
 
     @Override
     public int hashCode() {
+        // hashCode it is not implemented in R. Therefore it would be dangerous for
+        // NetworkStack to depend on it.
         return Objects.hash(apfVersionSupported, maximumApfProgramSize, apfPacketFormat);
     }