diff --git a/zip/boinc_zip.cpp b/zip/boinc_zip.cpp
index 4d82c60d03..c7ba2baaf6 100644
--- a/zip/boinc_zip.cpp
+++ b/zip/boinc_zip.cpp
@@ -318,7 +318,8 @@ boinc_UnzipToMemory ( char *zip, char *file, string &retstr )
   funcs.inputfn = (InputFn *)scanf;
   funcs.pausefn = (PauseFn *)( 0x01 );
   funcs.passwdfn = (PasswdFn *)( NULL );
-  
+
+  memset( &buf, 0, sizeof(buf) );	// data-blocks needs to be empty
   ret = UzpUnzipToMemory( zip, file, &opts, &funcs, &buf );
 
   if ( ret )