diff --git a/src/main/java/org/apache/maven/plugins/pmd/PmdReportRenderer.java b/src/main/java/org/apache/maven/plugins/pmd/PmdReportRenderer.java
index d961eebb..ebbf1faf 100644
--- a/src/main/java/org/apache/maven/plugins/pmd/PmdReportRenderer.java
+++ b/src/main/java/org/apache/maven/plugins/pmd/PmdReportRenderer.java
@@ -410,7 +410,7 @@ private String shortenFilename(String filename, PmdFileInfo fileInfo) {
             result = StringUtils.substring(
                     result, fileInfo.getSourceDirectory().getAbsolutePath().length() + 1);
         }
-        return StringUtils.replace(result, "\\", "/");
+        return result == null || result.isEmpty() ? result : result.replace("\\", "/");
     }
 
     private String makeFileSectionName(String filename, PmdFileInfo fileInfo) {