diff --git a/gen/asm-x86-32.h b/gen/asm-x86-32.h
index 0edbe613..b2f06c77 100644
--- a/gen/asm-x86-32.h
+++ b/gen/asm-x86-32.h
@@ -1821,9 +1821,9 @@ namespace AsmParserx8632
             else if ( op == Op_FMath0 || op == Op_FdST0ST1 )
             {
                 operands[0].cls = Opr_Reg;
-                operands[0].reg = Reg_ST;
+                operands[0].reg = Reg_ST1;
                 operands[1].cls = Opr_Reg;
-                operands[1].reg = Reg_ST1;
+                operands[1].reg = Reg_ST;
                 nOperands = 2;
             }
 
diff --git a/gen/asm-x86-64.h b/gen/asm-x86-64.h
index 3fef6e05..3060da0c 100644
--- a/gen/asm-x86-64.h
+++ b/gen/asm-x86-64.h
@@ -1943,9 +1943,9 @@ namespace AsmParserx8664
             else if ( op == Op_FMath0 || op == Op_FdST0ST1 )
             {
                 operands[0].cls = Opr_Reg;
-                operands[0].reg = Reg_ST;
+                operands[0].reg = Reg_ST1;
                 operands[1].cls = Opr_Reg;
-                operands[1].reg = Reg_ST1;
+                operands[1].reg = Reg_ST;
                 nOperands = 2;
             }