diff --git a/.baseline/checkstyle/checkstyle.xml b/.baseline/checkstyle/checkstyle.xml
index 268ebe3f..f541b63e 100644
--- a/.baseline/checkstyle/checkstyle.xml
+++ b/.baseline/checkstyle/checkstyle.xml
@@ -469,7 +469,7 @@
         <module name="NestedTryDepth"/> <!-- Java Coding Guide: Try/catch blocks: never nested -->
         <module name="NonEmptyAtclauseDescription"/> <!-- Java Style Guide: At-clauses -->
         <module name="ParameterName"> <!-- Java Style Guide: Parameter names -->
-            <property name="format" value="^[a-z][a-zA-Z0-9]+$"/>
+            <property name="format" value="^_?[a-z][a-zA-Z0-9]+$"/>
             <message key="name.invalidPattern" value="Parameter name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="SingleLineJavadoc"/> <!-- Java Style Guide: General form -->
diff --git a/build.gradle b/build.gradle
index 81a3a982..970055f7 100644
--- a/build.gradle
+++ b/build.gradle
@@ -12,7 +12,7 @@ buildscript {
     dependencies {
         classpath 'com.netflix.nebula:gradle-info-plugin:5.1.0'
         classpath 'com.netflix.nebula:nebula-publishing-plugin:13.6.0'
-        classpath 'com.palantir.baseline:gradle-baseline-java:2.9.0'
+        classpath 'com.palantir.baseline:gradle-baseline-java:2.9.1'
         classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.8.4'
         classpath 'com.palantir.gradle.gitversion:gradle-git-version:0.12.2'
     }