--- valgrind-3.7.0/coregrind/m_syswrap/syswrap-linux.c.jj	2010-04-07 08:14:12.000000000 -0400
+++ valgrind-3.7.0/coregrind/m_syswrap/syswrap-linux.c	2010-04-12 07:24:12.838876000 -0400
@@ -2212,8 +2212,9 @@ PRE(sys_capget)
                  vki_cap_user_header_t, header, vki_cap_user_data_t, data);
    PRE_MEM_READ( "capget(header)", ARG1, 
                   sizeof(struct __vki_user_cap_header_struct) );
-   PRE_MEM_WRITE( "capget(data)", ARG2, 
-                  sizeof(struct __vki_user_cap_data_struct) );
+   if (ARG2 != (Addr)NULL)
+      PRE_MEM_WRITE( "capget(data)", ARG2, 
+                      sizeof(struct __vki_user_cap_data_struct) );
 }
 POST(sys_capget)
 {