diff --git a/gen/asm-x86-32.h b/gen/asm-x86-32.h
index b6fc2a3e..75afc559 100644
--- a/gen/asm-x86-32.h
+++ b/gen/asm-x86-32.h
@@ -1869,7 +1869,7 @@ namespace AsmParserx8632
                 // special case fdiv, fsub: see dmd 840, ldc 256
                 if ((strncmp(mnemonic, "fsub", 4) == 0 ||
                      strncmp(mnemonic, "fdiv", 4) == 0) && 
-                    operands[0].reg != Reg_ST)
+                    operands[0].reg != Reg_ST && op != Op_FMath)
                 {
                     // replace:
                     //   f{sub,div}r{p,} <-> f{sub,div}{p,}
diff --git a/gen/asm-x86-64.h b/gen/asm-x86-64.h
index 6a4e8abf..b7c14584 100644
--- a/gen/asm-x86-64.h
+++ b/gen/asm-x86-64.h
@@ -1995,7 +1995,7 @@ namespace AsmParserx8664
                 // special case fdiv, fsub: see dmd 840, ldc 256
                 if ((strncmp(mnemonic, "fsub", 4) == 0 ||
                      strncmp(mnemonic, "fdiv", 4) == 0) && 
-                    operands[0].reg != Reg_ST)
+                    operands[0].reg != Reg_ST && op != Op_FMath)
                 {
                     // replace:
                     //   f{sub,div}r{p,} <-> f{sub,div}{p,}