diff --git a/src/libtriton/arch/x86/x8664Cpu.cpp b/src/libtriton/arch/x86/x8664Cpu.cpp
index ecabdbdc3..05b4f1b52 100644
--- a/src/libtriton/arch/x86/x8664Cpu.cpp
+++ b/src/libtriton/arch/x86/x8664Cpu.cpp
@@ -277,7 +277,7 @@ namespace triton {
 
 
       bool x8664Cpu::isFlag(triton::arch::register_e regId) const {
-        if (regId >= triton::arch::ID_REG_X86_AC       && regId <= triton::arch::ID_REG_X86_FSW_B)    { return true; }
+        if (regId >= triton::arch::ID_REG_X86_AC       && regId <= triton::arch::ID_REG_X86_ZF)       { return true; }
         if (regId >= triton::arch::ID_REG_X86_FTW      && regId <= triton::arch::ID_REG_X86_FDP)      { return true; }
         if (regId >= triton::arch::ID_REG_X86_SSE_IE   && regId <= triton::arch::ID_REG_X86_SSE_FZ)   { return true; }
         if (regId >= triton::arch::ID_REG_X86_FCW_IM   && regId <= triton::arch::ID_REG_X86_FCW_X)    { return true; }
@@ -336,7 +336,7 @@ namespace triton {
 
 
       bool x8664Cpu::isEFER(triton::arch::register_e regId) const {
-        return ((regId >= triton::arch::ID_REG_X86_EFER && regId <= triton::arch::ID_REG_X86_EFER) ? true : false);
+        return ((regId == triton::arch::ID_REG_X86_EFER) ? true : false);
       }
 
 
diff --git a/src/libtriton/arch/x86/x86Cpu.cpp b/src/libtriton/arch/x86/x86Cpu.cpp
index d303fefc8..3b50fc587 100644
--- a/src/libtriton/arch/x86/x86Cpu.cpp
+++ b/src/libtriton/arch/x86/x86Cpu.cpp
@@ -213,7 +213,7 @@ namespace triton {
 
 
       bool x86Cpu::isFlag(triton::arch::register_e regId) const {
-        if (regId >= triton::arch::ID_REG_X86_AC     && regId <= triton::arch::ID_REG_X86_FSW_B)  { return true; }
+        if (regId >= triton::arch::ID_REG_X86_AC     && regId <= triton::arch::ID_REG_X86_ZF)     { return true; }
         if (regId >= triton::arch::ID_REG_X86_FTW    && regId <= triton::arch::ID_REG_X86_FDP)    { return true; }
         if (regId >= triton::arch::ID_REG_X86_SSE_IE && regId <= triton::arch::ID_REG_X86_SSE_FZ) { return true; }
         if (regId >= triton::arch::ID_REG_X86_FCW_IM && regId <= triton::arch::ID_REG_X86_FCW_X)  { return true; }
@@ -269,7 +269,7 @@ namespace triton {
 
 
       bool x86Cpu::isEFER(triton::arch::register_e regId) const {
-        return ((regId >= triton::arch::ID_REG_X86_EFER && regId <= triton::arch::ID_REG_X86_EFER) ? true : false);
+        return ((regId == triton::arch::ID_REG_X86_EFER) ? true : false);
       }