diff --git a/arch/x86_64/bits/signal.h b/arch/x86_64/bits/signal.h
index e3c3141..5393649 100644
--- a/arch/x86_64/bits/signal.h
+++ b/arch/x86_64/bits/signal.h
@@ -33,6 +33,14 @@
 #endif
 
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
+#define FP_XSTATE_MAGIC1 0x46505853U
+#define FP_XSTATE_MAGIC2 0x46505845U
+#define FP_XSTATE_MAGIC2_SIZE 4UL
+struct _fpx_sw_bytes {
+	unsigned magic1, extended_size;
+	unsigned long xstate_bv;
+	unsigned xstate_size, padding[7];
+};
 typedef long long greg_t, gregset_t[23];
 typedef struct _fpstate {
 	unsigned short cwd, swd, ftw, fop;