diff --git a/src/main/java/com/databasepreservation/common/transformers/ToolkitStructure2ViewerStructure.java b/src/main/java/com/databasepreservation/common/transformers/ToolkitStructure2ViewerStructure.java
index 435b20a7..d15a9ede 100644
--- a/src/main/java/com/databasepreservation/common/transformers/ToolkitStructure2ViewerStructure.java
+++ b/src/main/java/com/databasepreservation/common/transformers/ToolkitStructure2ViewerStructure.java
@@ -938,6 +938,7 @@ private static void detectMimeType(ViewerRow row, ViewerCell cell, String databa
         }
       }
 
+      inputStream.close();
       zipFile.close();
 
       cell.setMimeType(mimeType);