diff --git a/httpclient-cache/pom.xml b/httpclient-cache/pom.xml
index f8bbd4193..faf7a9133 100644
--- a/httpclient-cache/pom.xml
+++ b/httpclient-cache/pom.xml
@@ -111,6 +111,14 @@
     <maven.compile.target>1.5</maven.compile.target>
     <maven.compile.optimize>true</maven.compile.optimize>
     <maven.compile.deprecation>true</maven.compile.deprecation>
+    <!-- cache was not present in 4.0; it first appeared in 4.1-alpha2 -->
+    <comparisonVersion>4.1-alpha2</comparisonVersion>
+    <!-- 
+     -- Allow separate override of cache version, e.g.
+     --
+     -- mvn clirr:clirr -DcomparisonVersion=4.1-alpha1 -Dcache.comparisonVersion=4.1-alpha2
+     -->
+    <cache.comparisonVersion>${comparisonVersion}</cache.comparisonVersion>
   </properties>
 
   <build>
@@ -172,6 +180,13 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>clirr-maven-plugin</artifactId>
+        <configuration>
+          <comparisonVersion>${cache.comparisonVersion}</comparisonVersion>
+        </configuration>
+      </plugin>
     </plugins>
   </build>
 
diff --git a/httpclient/pom.xml b/httpclient/pom.xml
index 3d8417f66..3324910e9 100644
--- a/httpclient/pom.xml
+++ b/httpclient/pom.xml
@@ -186,14 +186,6 @@
         </configuration>
       </plugin>
 
-      <plugin>
-        <groupId>org.codehaus.mojo</groupId>
-        <artifactId>clirr-maven-plugin</artifactId>
-        <configuration>
-          <comparisonVersion>4.0</comparisonVersion>
-        </configuration>
-      </plugin>
-
       <plugin>
         <artifactId>maven-jxr-plugin</artifactId>
       </plugin>
diff --git a/pom.xml b/pom.xml
index 4dbe58243..6116dd6d5 100644
--- a/pom.xml
+++ b/pom.xml
@@ -75,6 +75,7 @@
     <slf4j.version>1.5.11</slf4j.version>
     <junit.version>4.8.1</junit.version>
     <easymock.version>2.5.2</easymock.version>
+    <comparisonVersion>4.0</comparisonVersion>
   </properties>
 
   <modules>
@@ -225,6 +226,13 @@
             </execution>
           </executions>
         </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>clirr-maven-plugin</artifactId>
+        <configuration>
+          <comparisonVersion>${comparisonVersion}</comparisonVersion>
+        </configuration>
+      </plugin>
     </plugins>
   </build>
 
@@ -246,6 +254,14 @@
          </reportSets>
       </plugin>
 
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>clirr-maven-plugin</artifactId>
+        <configuration>
+          <comparisonVersion>${comparisonVersion}</comparisonVersion>
+        </configuration>
+      </plugin>
+
     </plugins>
   </reporting>