diff --git a/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java b/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java
index 26ea1b0c7..3ddfc7803 100644
--- a/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java
+++ b/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java
@@ -338,8 +338,9 @@ public abstract class ContentTypeManager {
          */
         if (this.container != null && this.container.getPart(partName) != null) {
             throw new OpenXML4JRuntimeException(
-                    "Rule M2.4 exception : Part \'" + partName +
-                            "\' not found - this error should NEVER happen! If you can provide the triggering file, then please raise a bug at https://bz.apache.org/bugzilla/enter_bug.cgi?product=POI and attach the file that triggers it, thanks!");
+                 "Rule M2.4 exception : this error should NEVER happen!\n"
+                 + "Check that your code is closing the open resources in the correct order prior to filing a bug report.\n"
+                 + "If you can provide the triggering file, then please raise a bug at https://bz.apache.org/bugzilla/enter_bug.cgi?product=POI and attach the file that triggers it, thanks!");
         }
         return null;
     }