diff --git a/lib/asm/x86-64/X86_64Assembler.v3 b/lib/asm/x86-64/X86_64Assembler.v3
index 36333e020..f7e2a0dd7 100644
--- a/lib/asm/x86-64/X86_64Assembler.v3
+++ b/lib/asm/x86-64/X86_64Assembler.v3
@@ -1001,6 +1001,20 @@ class X86_64Assembler(w: DataWriter, OP_REX: byte) {
 	def negq_m(a: X86_64Addr) -> this {
 		emit_rex_b_m_x(a, REX_W, 0xF7, 3);
 	}
+        def negb_r(a: X86_64Gpr) -> this {
+                emit_rex_b_r_x(a, NO_REX, 0xF6, 3);
+        }
+        def negw_r(a: X86_64Gpr) -> this {
+                emitb(PREFIX_W);
+                emit_rex_b_r_x(a, NO_REX, 0xF7, 3);
+        }
+        def negd_r(a: X86_64Gpr) -> this {
+                emit_rex_b_r_x(a, NO_REX, 0xF7, 3);
+        }
+        def negq_r(a: X86_64Gpr) -> this {
+                emit_rex_b_r_x(a, REX_W, 0xF7, 3);
+        }
+
 	def pushq_m(a: X86_64Addr) -> this {
 		emit_rex_b_m_x(a, NO_REX, 0xFF, 6);
 	}
diff --git a/test/asm/x86-64/X86_64AssemblerTestGen.v3 b/test/asm/x86-64/X86_64AssemblerTestGen.v3
index 061f68381..17238e4d2 100644
--- a/test/asm/x86-64/X86_64AssemblerTestGen.v3
+++ b/test/asm/x86-64/X86_64AssemblerTestGen.v3
@@ -125,7 +125,7 @@ def main(a: Array<string>) -> int {
 	do_orn();
 	do_andn();
 	do_negn();
-
+	do_negn_r();
 	do_r_dq("xchg", do_r_r, asm.d.xchg_r_r, asm.q.xchg_r_r);
 	do_m_dq("xchg", do_m_r, asm.d.xchg_m_r, asm.q.xchg_m_r);
 	do_r_dq("xadd", do_r_r, asm.d.xadd_r_r, asm.q.xadd_r_r);
@@ -406,6 +406,17 @@ def do_negn() {
 	do_m("neg qword", asm.negq_m);
 }
 
+def do_negn_r() {
+ 	regSize = 8;
+ 	do_r("and byte", asm.negb_r);
+ 	regSize = 16;
+ 	do_r("and word", asm.negw_r);
+ 	regSize = 32;
+ 	do_r("and dword", asm.negd_r);
+ 	regSize = 64;
+ 	do_r("and qword", asm.negq_r);
+ }
+
 def do_set() {
 	var buf = StringBuilder.new();
 	for (cond in X86_64Conds.all) {