diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 9446ec35841fc1389d8893273919bb2fad7f0bd1..3a1973de13db4a0b455d4ecd777c9bacb6d7d963 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -25920,7 +25920,8 @@
   "TARGET_64BIT && TARGET_FSGSBASE"
   "rd<fsgs>base\t%0"
   [(set_attr "type" "other")
-   (set_attr "prefix_extra" "2")])
+   (set_attr "prefix_0f" "1")
+   (set_attr "prefix_rep" "1")])
 
 (define_insn "wr<fsgs>base<mode>"
   [(unspec_volatile [(match_operand:SWI48 0 "register_operand" "r")]
@@ -25928,7 +25929,8 @@
   "TARGET_64BIT && TARGET_FSGSBASE"
   "wr<fsgs>base\t%0"
   [(set_attr "type" "other")
-   (set_attr "prefix_extra" "2")])
+   (set_attr "prefix_0f" "1")
+   (set_attr "prefix_rep" "1")])
 
 (define_insn "ptwrite<mode>"
   [(unspec_volatile [(match_operand:SWI48 0 "nonimmediate_operand" "rm")]
@@ -25936,7 +25938,8 @@
   "TARGET_PTWRITE"
   "ptwrite\t%0"
   [(set_attr "type" "other")
-   (set_attr "prefix_extra" "2")])
+   (set_attr "prefix_0f" "1")
+   (set_attr "prefix_rep" "1")])
 
 (define_insn "@rdrand<mode>"
   [(set (match_operand:SWI248 0 "register_operand" "=r")