diff --git a/criu/arch/aarch64/include/asm/infect-types.h b/criu/arch/aarch64/include/asm/infect-types.h
index 76fcfebf5..714881c57 100644
--- a/criu/arch/aarch64/include/asm/infect-types.h
+++ b/criu/arch/aarch64/include/asm/infect-types.h
@@ -23,6 +23,8 @@ typedef struct user_fpsimd_state	user_fpregs_struct_t;
 #define REG_IP(r)			((uint64_t)(r).pc)
 #define REG_SYSCALL_NR(r)		((uint64_t)(r).regs[8])
 
+#define user_regs_native(pregs)			true
+
 /*
  * Range for task size calculated from the following Linux kernel files:
  *   arch/arm64/include/asm/memory.h
diff --git a/criu/arch/arm/include/asm/infect-types.h b/criu/arch/arm/include/asm/infect-types.h
index 3552ec931..9c2092e5d 100644
--- a/criu/arch/arm/include/asm/infect-types.h
+++ b/criu/arch/arm/include/asm/infect-types.h
@@ -57,6 +57,8 @@ struct user_vfp_exc {
 #define REG_IP(regs)		((regs).ARM_pc)
 #define REG_SYSCALL_NR(regs)	((regs).ARM_r7)
 
+#define user_regs_native(pregs)			true
+
 /*
  * Range for task size calculated from the following Linux kernel files:
  *   arch/arm/include/asm/memory.h
diff --git a/criu/arch/ppc64/include/asm/infect-types.h b/criu/arch/ppc64/include/asm/infect-types.h
index 1969ca2b5..f243def73 100644
--- a/criu/arch/ppc64/include/asm/infect-types.h
+++ b/criu/arch/ppc64/include/asm/infect-types.h
@@ -76,6 +76,8 @@ typedef struct {
 #define REG_IP(regs)		((uint64_t)(regs).nip)
 #define REG_SYSCALL_NR(regs)	((uint64_t)(regs).gpr[0])
 
+#define user_regs_native(pregs)			true
+
 /*
  * Copied from the following kernel header files :
  * 	include/linux/auxvec.h
diff --git a/criu/arch/x86/crtools.c b/criu/arch/x86/crtools.c
index 85f2f54ed..f48aa82de 100644
--- a/criu/arch/x86/crtools.c
+++ b/criu/arch/x86/crtools.c
@@ -67,7 +67,7 @@ int arch_task_compatible(pid_t pid)
 	if (ret)
 		return -1;
 
-	return !r.is_native;
+	return !user_regs_native(&r);
 }
 
 #define USER32_CS	0x23
@@ -120,7 +120,7 @@ int syscall_seized(struct parasite_ctl *ctl, int nr, unsigned long *ret,
 	user_regs_struct_t regs = ctl->orig.regs;
 	int err;
 
-	if (regs.is_native) {
+	if (user_regs_native(&regs)) {
 		user_regs_struct64 *r = &regs.native;
 
 		r->ax  = (uint64_t)nr;
@@ -152,7 +152,7 @@ static int save_task_regs(CoreEntry *core,
 		user_regs_struct_t *regs, user_fpregs_struct_t *fpregs);
 
 #define get_signed_user_reg(pregs, name)				\
-	(((pregs)->is_native) ? (int64_t)((pregs)->native.name) :	\
+	((user_regs_native(pregs)) ? (int64_t)((pregs)->native.name) :	\
 				(int32_t)((pregs)->compat.name))
 int get_task_regs(pid_t pid, user_regs_struct_t regs, CoreEntry *core)
 {
@@ -222,7 +222,7 @@ static int save_task_regs(CoreEntry *core,
 #define assign_reg(dst, src, e)		do { dst->e = (__typeof__(dst->e))src.e; } while (0)
 #define assign_array(dst, src, e)	memcpy(dst->e, &src.e, sizeof(src.e))
 
-	if (regs.is_native) {
+	if (user_regs_native(regs)) {
 		assign_reg(gpregs, regs->native, r15);
 		assign_reg(gpregs, regs->native, r14);
 		assign_reg(gpregs, regs->native, r13);
@@ -314,11 +314,11 @@ int ptrace_get_regs(pid_t pid, user_regs_struct_t *regs)
 
 	ret = ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov);
 	if (iov.iov_len == sizeof(regs->native)) {
-		regs->is_native = true;
+		regs->__is_native = NATIVE_MAGIC;
 		return ret;
 	}
 	if (iov.iov_len == sizeof(regs->compat)) {
-		regs->is_native = false;
+		regs->__is_native = COMPAT_MAGIC;
 		return ret;
 	}
 
@@ -332,7 +332,7 @@ int ptrace_set_regs(pid_t pid, user_regs_struct_t *regs)
 {
 	struct iovec iov;
 
-	if (regs->is_native) {
+	if (user_regs_native(regs)) {
 		iov.iov_base = &regs->native;
 		iov.iov_len = sizeof(user_regs_struct64);
 	} else {
diff --git a/criu/arch/x86/include/asm/infect-types.h b/criu/arch/x86/include/asm/infect-types.h
index d56902acf..08344f747 100644
--- a/criu/arch/x86/include/asm/infect-types.h
+++ b/criu/arch/x86/include/asm/infect-types.h
@@ -4,6 +4,8 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <signal.h>
+#include "log.h"
+#include "common/bug.h"
 #include "common/page.h"
 #include "syscall-types.h"
 
@@ -61,27 +63,45 @@ typedef struct {
 } user_regs_struct32;
 
 #ifdef CONFIG_X86_64
+/*
+ * To be sure that we rely on inited reg->__is_native, this member
+ * is (short int) instead of initial (bool). The right way to
+ * check if regs are native or compat is to use user_regs_native() macro.
+ * This should cost nothing, as *usually* sizeof(bool) == sizeof(short)
+ */
 typedef struct {
 	union {
 		user_regs_struct64 native;
 		user_regs_struct32 compat;
 	};
-	bool is_native;
+	short __is_native; /* use user_regs_native macro to check it */
 } user_regs_struct_t;
-#define get_user_reg(pregs, name) (((pregs)->is_native) ?	\
-		((pregs)->native.name) :			\
-		((pregs)->compat.name))
-#define set_user_reg(pregs, name, val) (((pregs)->is_native) ?	\
-		((pregs)->native.name = val) :			\
-		((pregs)->compat.name = val))
+
+#define NATIVE_MAGIC	0x0A
+#define COMPAT_MAGIC	0x0C
+static inline bool user_regs_native(user_regs_struct_t *pregs)
+{
+	return pregs->__is_native == NATIVE_MAGIC;
+}
+
+#define get_user_reg(pregs, name)			\
+	((user_regs_native(pregs))		?	\
+	 ((pregs)->native.name)			:	\
+	 ((pregs)->compat.name))
+
+#define set_user_reg(pregs, name, val)			\
+	((user_regs_native(pregs))		?	\
+	 ((pregs)->native.name = (val))		:	\
+	 ((pregs)->compat.name = (val)))
 #else
 typedef struct {
 	union {
 		user_regs_struct32 native;
 	};
 } user_regs_struct_t;
-#define get_user_reg(pregs, name) ((pregs)->native.name)
-#define set_user_reg(pregs, name, val) ((pregs)->native.name = val)
+#define user_regs_native(pregs)		true
+#define get_user_reg(pregs, name)	((pregs)->native.name)
+#define set_user_reg(pregs, name, val)	((pregs)->native.name = val)
 #endif
 
 #if 0