diff --git a/coregrind/vg_syscalls.c b/coregrind/vg_syscalls.c
index 3f634da19..cbe882d48 100644
--- a/coregrind/vg_syscalls.c
+++ b/coregrind/vg_syscalls.c
@@ -2861,11 +2861,11 @@ PRE(ioctl)
    case VKI_TCSETSW:
    case VKI_TCSETSF:
       SYSCALL_TRACK( pre_mem_read, tid, "ioctl(TCSET{S,SW,SF})", arg3, 
-		     VKI_SIZEOF_STRUCT_TERMIOS );
+		     sizeof(struct vki_termios) );
       break; 
    case VKI_TCGETS:
       SYSCALL_TRACK( pre_mem_write, tid, "ioctl(TCGETS)", arg3, 
-		     VKI_SIZEOF_STRUCT_TERMIOS );
+		     sizeof(struct vki_termios) );
       break;
    case VKI_TCSETA:
    case VKI_TCSETAW:
@@ -3571,7 +3571,7 @@ POST(ioctl)
    case VKI_TCSETSF:
       break; 
    case VKI_TCGETS:
-      VG_TRACK( post_mem_write, arg3, VKI_SIZEOF_STRUCT_TERMIOS );
+      VG_TRACK( post_mem_write, arg3, sizeof(struct vki_termios) );
       break;
    case VKI_TCSETA:
    case VKI_TCSETAW:
diff --git a/include/x86-linux/vki_arch.h b/include/x86-linux/vki_arch.h
index 2d50c253f..8a097e93b 100644
--- a/include/x86-linux/vki_arch.h
+++ b/include/x86-linux/vki_arch.h
@@ -406,7 +406,18 @@ struct vki_termio {
 // From linux-2.6.8.1/include/asm-i386/termbits.h
 //----------------------------------------------------------------------
 
-#define VKI_SIZEOF_STRUCT_TERMIOS	17
+typedef unsigned char   vki_cc_t;
+typedef unsigned int    vki_tcflag_t;
+
+#define VKI_NCCS 19
+struct vki_termios {
+	vki_tcflag_t c_iflag;		/* input mode flags */
+	vki_tcflag_t c_oflag;		/* output mode flags */
+	vki_tcflag_t c_cflag;		/* control mode flags */
+	vki_tcflag_t c_lflag;		/* local mode flags */
+	vki_cc_t c_line;		/* line discipline */
+	vki_cc_t c_cc[VKI_NCCS];	/* control characters */
+};
 
 //----------------------------------------------------------------------
 // From linux-2.6.8.1/include/asm-i386/ioctl.h