diff --git a/src/vaadin-checkbox-group.html b/src/vaadin-checkbox-group.html
index 94021db..d9e27e4 100644
--- a/src/vaadin-checkbox-group.html
+++ b/src/vaadin-checkbox-group.html
@@ -150,6 +150,7 @@
 
             /**
              * Error to show when the input value is invalid.
+             * @attr {string} error-message
              */
             errorMessage: {
               type: String,
@@ -159,6 +160,7 @@
 
             /**
              * String used for the helper text.
+             * @attr {string} helper-text
              * @type {string | null}
              */
             helperText: {