diff --git a/emu/gadgets-x86/bits.S b/emu/gadgets-x86/bits.S
index 04e047f7..2062c465 100644
--- a/emu/gadgets-x86/bits.S
+++ b/emu/gadgets-x86/bits.S
@@ -76,3 +76,12 @@
 .each_reg x
 .purgem x
 .gadget_array bt
+
+.macro x name reg
+    .gadget bswap_\name
+        bswap %\reg
+        gret
+.endm
+.each_reg x
+.purgem x
+.gadget_list bswap, REG_LIST
diff --git a/emu/gen.c b/emu/gen.c
index 6624dd88..5fd848ed 100644
--- a/emu/gen.c
+++ b/emu/gen.c
@@ -286,7 +286,7 @@ static inline bool gen_op(struct gen_state *state, gadget_t *gadgets, enum arg a
 #define BSF(src, dst,z) los(bsf, src, dst, z)
 #define BSR(src, dst,z) los(bsr, src, dst, z)
 
-#define BSWAP(dst) UNDEFINED
+#define BSWAP(dst) ga(bswap, arg_##dst)
 
 #define strop(op, rep, z) gag(op, sz(z) * size_count + rep_##rep, saved_ip)
 #define STR(op, z) strop(op, once, z)