diff --git a/src/65c02isa.csv b/src/65c02isa.csv
index bfa70de..7536420 100644
--- a/src/65c02isa.csv
+++ b/src/65c02isa.csv
@@ -99,7 +99,7 @@ OP_RTS,"rts",IMPLIED,1,NULL
 OP_ADC_IZPX,"adc",IZPX,2,NULL
 OP_NOPI_63,"nop",IMMEDIATE,2,NULL
 OP_NOPI_64,"nop",IMPLIED,1,NULL
-OP_STZ_ZP,"stz",ZP,2,NULL
+OP_STZ_ZP,"stz",ZP,2,emul_stz
 OP_ADC_ZP,"adc",ZP,2,NULL
 OP_ROR_ZP,"ror",ZP,2,NULL
 OP_RMB6_ZP,"rmb6",ZP,2,NULL
diff --git a/src/emulation.c b/src/emulation.c
index b57c4f1..16cae1a 100644
--- a/src/emulation.c
+++ b/src/emulation.c
@@ -63,3 +63,14 @@ emul_stp(rk65c02emu_t *e, instruction_t *i)
 	e->state = STOPPED;
 }
 
+/* STZ - store zero */
+void
+emul_stz(rk65c02emu_t *e, instruction_t *i)
+{
+	instrdef_t id;
+
+	id = instruction_decode(i->opcode);
+
+	instruction_data_write_1(e, &id, i, 0);
+}
+
diff --git a/test/Makefile b/test/Makefile
index 705586e..e5731f3 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -8,7 +8,8 @@ TESTS=test_bus test_emulation
 TESTROMS=test_emulation_and_imm.rom \
 	test_emulation_pha.rom test_emulation_pla.rom \
 	test_emulation_nop.rom \
-	test_emulation_lda_imm.rom test_emulation_lda_zp.rom
+	test_emulation_lda_imm.rom test_emulation_lda_zp.rom \
+	test_emulation_stz_zp.rom
 
 all : $(TESTS) $(TESTROMS)
 
diff --git a/test/test_emulation.c b/test/test_emulation.c
index 9e33f65..de645e7 100644
--- a/test/test_emulation.c
+++ b/test/test_emulation.c
@@ -45,6 +45,23 @@ ATF_TC_BODY(emul_lda, tc)
 	bus_finish(&b);
 }
 
+ATF_TC_WITHOUT_HEAD(emul_stz);
+ATF_TC_BODY(emul_stz, tc)
+{
+	rk65c02emu_t e;
+	bus_t b;
+
+	b = bus_init();
+	e = rk65c02_init(&b);
+
+	/* STZ zp */
+	bus_write_1(&b, 0x10, 0xAA);
+	ATF_REQUIRE(rom_start(&e, "test_emulation_stz_zp.rom"));
+	ATF_CHECK(bus_read_1(&b, 0x10) == 0x00);
+
+	bus_finish(&b);
+}
+
 ATF_TC_WITHOUT_HEAD(emul_and);
 ATF_TC_BODY(emul_and, tc)
 {
@@ -134,6 +151,8 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, emul_and);
 	ATF_TP_ADD_TC(tp, emul_lda);
 	ATF_TP_ADD_TC(tp, emul_nop);
+	ATF_TP_ADD_TC(tp, emul_stz);
+
 	ATF_TP_ADD_TC(tp, emul_stack);
 
 	return (atf_no_error());
diff --git a/test/test_emulation_stz_zp.s b/test/test_emulation_stz_zp.s
new file mode 100644
index 0000000..d4d0465
--- /dev/null
+++ b/test/test_emulation_stz_zp.s
@@ -0,0 +1,3 @@
+start:  stz 0x10
+	stp
+