diff --git a/config/jsoref-spellchecker/whitelist.words b/config/jsoref-spellchecker/whitelist.words
index 21c71e186d1..9efbfad7665 100644
--- a/config/jsoref-spellchecker/whitelist.words
+++ b/config/jsoref-spellchecker/whitelist.words
@@ -685,6 +685,7 @@ jhu
 jide
 jidesoft
 jira
+JIs
 jitpack
 jkl
 JLabel
diff --git a/pom.xml b/pom.xml
index 7ef5fc14175..c13687df381 100644
--- a/pom.xml
+++ b/pom.xml
@@ -239,6 +239,7 @@
     <doxia.version>1.12.0</doxia.version>
     <error-prone.configuration-args>
       -Xep:AmbiguousJsonCreator:ERROR
+      -Xep:AssertJIsNull:ERROR
       <!-- Reason at https://github.com/checkstyle/checkstyle/issues/8252. -->
       -Xep:JUnitClassModifiers:OFF
       <!-- Reason at https://github.com/checkstyle/checkstyle/issues/8252. -->