diff --git a/datafiles/avx512f/avx512-reg-table-mask.txt b/datafiles/avx512f/avx512-reg-table-mask.txt
index 3a8e2a8..0b99b92 100644
--- a/datafiles/avx512f/avx512-reg-table-mask.txt
+++ b/datafiles/avx512f/avx512-reg-table-mask.txt
@@ -50,16 +50,19 @@ REXRR=0 REXR=0 REG=0x5 | OUTREG=XED_REG_K5
 REXRR=0 REXR=0 REG=0x6 | OUTREG=XED_REG_K6
 REXRR=0 REXR=0 REG=0x7 | OUTREG=XED_REG_K7
 
-# only used in VEX space for K-mask ops
+# MASK_B is used by VEX and EVEX encodings. SDM (rev 062) states in
+# EVEX, EVEX.B (REXB) is ignored. SDM does not (yet) say what happens
+# on VEX.B but assuming it is similar.
+
 xed_reg_enum_t MASK_B()::
-REXB=0 RM=0x0 | OUTREG=XED_REG_K0
-REXB=0 RM=0x1 | OUTREG=XED_REG_K1
-REXB=0 RM=0x2 | OUTREG=XED_REG_K2
-REXB=0 RM=0x3 | OUTREG=XED_REG_K3
-REXB=0 RM=0x4 | OUTREG=XED_REG_K4
-REXB=0 RM=0x5 | OUTREG=XED_REG_K5
-REXB=0 RM=0x6 | OUTREG=XED_REG_K6
-REXB=0 RM=0x7 | OUTREG=XED_REG_K7
+RM=0x0 | OUTREG=XED_REG_K0
+RM=0x1 | OUTREG=XED_REG_K1
+RM=0x2 | OUTREG=XED_REG_K2
+RM=0x3 | OUTREG=XED_REG_K3
+RM=0x4 | OUTREG=XED_REG_K4
+RM=0x5 | OUTREG=XED_REG_K5
+RM=0x6 | OUTREG=XED_REG_K6
+RM=0x7 | OUTREG=XED_REG_K7
 
 # only used in VEX space for K-mask ops
 # stored inverted
diff --git a/src/dec/xed-ild.c b/src/dec/xed-ild.c
index 5667648..ddb7f6a 100644
--- a/src/dec/xed-ild.c
+++ b/src/dec/xed-ild.c
@@ -1347,13 +1347,12 @@ static void evex_scanner(xed_decoded_inst_t* d)
             evex2.u32 = xed_decoded_inst_get_byte(d, length+2);
 
             // above check guarantees that r and x are 1 in 16/32b mode.
-            xed3_operand_set_rexr(d,  ~evex1.s.r_inv&1);
-            xed3_operand_set_rexx(d,  ~evex1.s.x_inv&1);
-
-            // force rexb to zero in 16/32b mode because it can be used for gprs
-            xed3_operand_set_rexb(d,  (xed3_mode_64b(d) & ~evex1.s.b_inv)&1);
-            // rexrr not used for gprs. Only for evex x/y/zmm regs
-            xed3_operand_set_rexrr(d, ~evex1.s.rr_inv&1);
+            if (xed3_mode_64b(d)) {
+                xed3_operand_set_rexr(d,  ~evex1.s.r_inv&1);
+                xed3_operand_set_rexx(d,  ~evex1.s.x_inv&1);
+                xed3_operand_set_rexb(d,  ~evex1.s.b_inv&1);
+                xed3_operand_set_rexrr(d, ~evex1.s.rr_inv&1);
+            }
             
             xed3_operand_set_map(d, evex1.s.map);