diff --git a/src/codegen/codegen_ops_x86-64.h b/src/codegen/codegen_ops_x86-64.h
index 129d9a740..5d6a62c7a 100644
--- a/src/codegen/codegen_ops_x86-64.h
+++ b/src/codegen/codegen_ops_x86-64.h
@@ -3875,19 +3875,31 @@ FP_LOAD_IMM_Q(uint64_t v)
 static __inline void
 FP_FCHS(void)
 {
+    addbyte(0x48); /* MOVABS RAX, 0x8000000000000000 */
+    addbyte(0xb8);
+    addquad(0x8000000000000000);
+    addbyte(0x66); /* MOVQ XMM15, RAX */
+    addbyte(0x4c);
+    addbyte(0x0f);
+    addbyte(0x6e);
+    addbyte(0xf8);
+    addbyte(0x48); /* XOR RAX, RAX */
+    addbyte(0x31);
+    addbyte(0xc0);
     addbyte(0x8b); /*MOV EAX, TOP*/
     addbyte(0x45);
     addbyte((uint8_t) cpu_state_offset(TOP));
-    addbyte(0xf2); /*SUBSD XMM0, XMM0*/
+    addbyte(0xf3); /*MOVQ XMM0, ST[EAX*8]*/
     addbyte(0x0f);
-    addbyte(0x5c);
-    addbyte(0xc0);
-    addbyte(0xf2); /*SUBSD XMM0, ST[EAX*8]*/
-    addbyte(0x0f);
-    addbyte(0x5c);
+    addbyte(0x7e);
     addbyte(0x44);
     addbyte(0xc5);
     addbyte((uint8_t) cpu_state_offset(ST));
+    addbyte(0x66); /* PXOR XMM0, XMM15 */
+    addbyte(0x41);
+    addbyte(0x0F);
+    addbyte(0xEF);
+    addbyte(0xC7);
     addbyte(0x80); /*AND tag[EAX], ~TAG_UINT64*/
     addbyte(0x64);
     addbyte(0x05);
diff --git a/src/codegen_new/codegen_backend_x86-64_uops.c b/src/codegen_new/codegen_backend_x86-64_uops.c
index 6b68434a0..356c8bcde 100644
--- a/src/codegen_new/codegen_backend_x86-64_uops.c
+++ b/src/codegen_new/codegen_backend_x86-64_uops.c
@@ -636,9 +636,10 @@ codegen_FCHS(codeblock_t *block, uop_t *uop)
     int src_size_a = IREG_GET_SIZE(uop->src_reg_a_real);
 
     if (REG_IS_D(dest_size) && REG_IS_D(src_size_a)) {
-        host_x86_MOVQ_XREG_XREG(block, REG_XMM_TEMP, src_reg_a);
-        host_x86_PXOR_XREG_XREG(block, dest_reg, dest_reg);
-        host_x86_SUBSD_XREG_XREG(block, dest_reg, REG_XMM_TEMP);
+        host_x86_MOVQ_XREG_XREG(block, dest_reg, src_reg_a);
+        host_x86_MOV64_REG_IMM(block, REG_RCX, 0x8000000000000000);
+        host_x86_MOVQ_XREG_REG(block, REG_XMM_TEMP, REG_RCX);
+        host_x86_PXOR_XREG_XREG(block, dest_reg, REG_XMM_TEMP);
     }
 #    ifdef RECOMPILER_DEBUG
     else