diff --git a/tools/testing/selftests/x86/mpx-hw.h b/tools/testing/selftests/x86/mpx-hw.h
index 3f0093911f03d5e474d245c4b4e37064643e917b..d1b61ab870f8d9f4d78412b48322f5f58bd5cd76 100644
--- a/tools/testing/selftests/x86/mpx-hw.h
+++ b/tools/testing/selftests/x86/mpx-hw.h
@@ -52,14 +52,14 @@
 struct mpx_bd_entry {
 	union {
 		char x[MPX_BOUNDS_DIR_ENTRY_SIZE_BYTES];
-		void *contents[1];
+		void *contents[0];
 	};
 } __attribute__((packed));
 
 struct mpx_bt_entry {
 	union {
 		char x[MPX_BOUNDS_TABLE_ENTRY_SIZE_BYTES];
-		unsigned long contents[1];
+		unsigned long contents[0];
 	};
 } __attribute__((packed));