diff --git a/assemble.c b/assemble.c
index e9cd70f8..a07bddec 100644
--- a/assemble.c
+++ b/assemble.c
@@ -1323,7 +1323,7 @@ static int64_t calcsize(int32_t segment, int64_t offset, int bits,
             length += 3;
         else
             length += 2;
-    } else if (ins->rex & REX_REAL) {
+    } else if (ins->rex & REX_MASK) {
         if (ins->rex & REX_H) {
             errfunc(ERR_NONFATAL, "cannot use high register in rex instruction");
             return -1;
@@ -1365,8 +1365,8 @@ static int64_t calcsize(int32_t segment, int64_t offset, int bits,
 static inline unsigned int emit_rex(insn *ins, int32_t segment, int64_t offset, int bits)
 {
     if (bits == 64) {
-        if ((ins->rex & REX_REAL) && !(ins->rex & (REX_V | REX_EV))) {
-            int rex = (ins->rex & REX_REAL) | REX_P;
+        if ((ins->rex & REX_MASK) && !(ins->rex & (REX_V | REX_EV))) {
+            int rex = (ins->rex & REX_MASK) | REX_P;
             out(offset, segment, &rex, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
             return 1;
         }
diff --git a/nasm.h b/nasm.h
index 18de37c8..48e4b1f0 100644
--- a/nasm.h
+++ b/nasm.h
@@ -500,7 +500,7 @@ static inline uint8_t get_cond_opcode(enum ccode c)
 /*
  * REX flags
  */
-#define REX_REAL    0x4f    /* Actual REX prefix bits */
+#define REX_MASK    0x4f    /* Actual REX prefix bits */
 #define REX_B       0x01    /* ModRM r/m extension */
 #define REX_X       0x02    /* SIB index extension */
 #define REX_R       0x04    /* ModRM reg extension */