diff --git a/tools/wordcloud/wordcloud.xml b/tools/wordcloud/wordcloud.xml
index a2792f3292..7703f3a059 100644
--- a/tools/wordcloud/wordcloud.xml
+++ b/tools/wordcloud/wordcloud.xml
@@ -163,7 +163,7 @@
         <test expect_num_outputs="1">
             <param name="text" value="test.txt" ftype="txt"/>
             <param name="random_state" value="10"/>
-            <output name="output" file="output_1.png"/>
+            <output name="output" file="output_1.png" compare="image_diff" />
         </test>
         <test expect_num_outputs="1">
             <param name="text" value="test.txt" ftype="txt"/>
@@ -192,7 +192,7 @@
             <param name="no_normalize_plurals" value="True"/>
             <param name="repeat" value="True"/>
             <param name="random_state" value="10"/>
-            <output name="output" file="output_2.png"/>
+            <output name="output" file="output_2.png" compare="image_diff" />
         </test>
     </tests>
     <help><![CDATA[