diff --git a/sscanApp/src/writeXDR.h b/sscanApp/src/writeXDR.h
index 9ac3a1f..e9e338b 100644
--- a/sscanApp/src/writeXDR.h
+++ b/sscanApp/src/writeXDR.h
@@ -2,7 +2,7 @@
 #include <stdio.h>
 #include <epicsTypes.h>
 
-typedef int (*xdrproc_t)();
+typedef int (*xdrproc_t)(FILE*, char*);
 
 extern int write_XDR_Init();
 extern int writeXDR_char(FILE *fd, char *cp);