diff --git a/include/ddk/wdm.h b/include/ddk/wdm.h
index c78e2da..0e26ac2 100644
--- a/include/ddk/wdm.h
+++ b/include/ddk/wdm.h
@@ -88,6 +88,7 @@
 typedef struct _ETHREAD *PETHREAD;
 typedef struct _KTHREAD *PKTHREAD;
 typedef struct _EPROCESS *PEPROCESS;
+typedef struct _IO_WORKITEM *PIO_WORKITEM;
 
 #define MAXIMUM_VOLUME_LABEL_LENGTH       (32 * sizeof(WCHAR))