diff --git a/coregrind/m_syswrap/syswrap-amd64-linux.c b/coregrind/m_syswrap/syswrap-amd64-linux.c

index 0f2ad8c51..407af7f76 100644

--- a/coregrind/m_syswrap/syswrap-amd64-linux.c

+++ b/coregrind/m_syswrap/syswrap-amd64-linux.c

@@ -249,6 +249,7 @@ PRE(sys_rt_sigreturn)

 PRE(sys_arch_prctl)

 {

    ThreadState* tst;

+   Bool known_option = True;

    PRINT( "arch_prctl ( %ld, %lx )", SARG1, ARG2 );

    vg_assert(VG_(is_valid_tid)(tid));

@@ -283,13 +284,16 @@ PRE(sys_arch_prctl)

       POST_MEM_WRITE(ARG2, sizeof(unsigned long));

    }

    else {

-      VG_(core_panic)("Unsupported arch_prctl option");

+      known_option = False;

    }

    /* Note; the Status writeback to guest state that happens after

       this wrapper returns does not change guest_FS_CONST or guest_GS_CONST;

       hence that direct assignment to the guest state is safe here. */

-   SET_STATUS_Success( 0 );

+   if (known_option)

+      SET_STATUS_Success( 0 );

+   else

+      SET_STATUS_Failure( VKI_EINVAL );

 }

 // Parts of this are amd64-specific, but the *PEEK* cases are generic.