diff --git a/src/65c02isa.csv b/src/65c02isa.csv
index 6bca62f..07ef7dc 100644
--- a/src/65c02isa.csv
+++ b/src/65c02isa.csv
@@ -87,7 +87,7 @@ OP_NOPI_55,"nop",ZPX,2,NULL,false
 OP_EOR_ZPX,"eor",ZPX,2,emul_eor,false
 OP_LSR_ZPX,"lsr",ZPX,2,emul_lsr,false
 OP_RMB5_ZP,"rmb5",ZP,2,emul_rmb5,false
-OP_CLI,"cli",IMPLIED,1,NULL,false
+OP_CLI,"cli",IMPLIED,1,emul_cli,false
 OP_EOR_ABSY,"eor",ABSOLUTEY,3,emul_eor,false
 OP_PHY,"phy",IMPLIED,1,emul_phy,false
 OP_NOPI_5C,"nop",IMPLIED,1,NULL,false
@@ -119,7 +119,7 @@ OP_STZ_ZPX,"stz",ZPX,2,emul_stz,false
 OP_ADC_ZPX,"adc",ZPX,2,NULL,false
 OP_ROR_ZPX,"ror",ZPX,2,emul_ror,false
 OP_RMB7_ZP,"rmb7",ZP,2,emul_rmb7,false
-OP_SEI,"sei",IMPLIED,1,NULL,false
+OP_SEI,"sei",IMPLIED,1,emul_sei,false
 OP_ADC_ABSY,"adc",ABSOLUTEY,3,NULL,false
 OP_PLY,"ply",IMPLIED,1,emul_ply,false
 OP_NOPI_7C,"nop",IMPLIED,1,NULL,false
diff --git a/src/emulation.c b/src/emulation.c
index e0bb186..04c3cd7 100644
--- a/src/emulation.c
+++ b/src/emulation.c
@@ -72,6 +72,13 @@ emul_clc(rk65c02emu_t *e, void *id, instruction_t *i)
 	e->regs.P &= ~P_CARRY;
 }
 
+/* CLI - clear interrupt disable flag */
+void
+emul_cli(rk65c02emu_t *e, void *id, instruction_t *i)
+{
+	e->regs.P &= ~P_IRQ_DISABLE;
+}
+
 /* CLV - clear overflow flag */
 void
 emul_clv(rk65c02emu_t *e, void *id, instruction_t *i)
@@ -446,6 +453,13 @@ emul_sec(rk65c02emu_t *e, void *id, instruction_t *i)
 	e->regs.P |= P_CARRY;
 }
 
+/* SEI - set the interrupt disable flag */
+void
+emul_sei(rk65c02emu_t *e, void *id, instruction_t *i)
+{
+	e->regs.P |= P_IRQ_DISABLE;
+}
+
 /* STP - stop the processor */
 void
 emul_stp(rk65c02emu_t *e, void *id, instruction_t *i)
diff --git a/test/test_emulation.c b/test/test_emulation.c
index 202eeda..5775f66 100644
--- a/test/test_emulation.c
+++ b/test/test_emulation.c
@@ -324,6 +324,25 @@ ATF_TC_BODY(emul_clc_sec, tc)
 	bus_finish(&b);
 }
 
+ATF_TC_WITHOUT_HEAD(emul_cli_sei);
+ATF_TC_BODY(emul_cli_sei, tc)
+{
+	rk65c02emu_t e;
+	bus_t b;
+
+	b = bus_init();
+	e = rk65c02_init(&b);
+
+	/* CLI */
+	ATF_REQUIRE(rom_start(&e, "test_emulation_cli.rom", tc));
+	ATF_CHECK(!(e.regs.P & P_IRQ_DISABLE));
+	/* SEI */
+	ATF_REQUIRE(rom_start(&e, "test_emulation_sei.rom", tc));
+	ATF_CHECK(e.regs.P & P_IRQ_DISABLE);
+
+	bus_finish(&b);
+}
+
 ATF_TC_WITHOUT_HEAD(emul_and);
 ATF_TC_BODY(emul_and, tc)
 {
@@ -682,6 +701,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, emul_dec);
 	ATF_TP_ADD_TC(tp, emul_dex_dey);
 	ATF_TP_ADD_TC(tp, emul_clc_sec);
+	ATF_TP_ADD_TC(tp, emul_cli_sei);
 	ATF_TP_ADD_TC(tp, emul_clv);
 	ATF_TP_ADD_TC(tp, emul_inc);
 	ATF_TP_ADD_TC(tp, emul_inx_iny);
diff --git a/test/test_emulation_cli.s b/test/test_emulation_cli.s
new file mode 100644
index 0000000..c061932
--- /dev/null
+++ b/test/test_emulation_cli.s
@@ -0,0 +1,3 @@
+start:  cli
+	stp
+
diff --git a/test/test_emulation_sei.s b/test/test_emulation_sei.s
new file mode 100644
index 0000000..7050152
--- /dev/null
+++ b/test/test_emulation_sei.s
@@ -0,0 +1,3 @@
+start:	sei
+	stp
+