diff --git a/src/devices/cpu/z80/z80.cpp b/src/devices/cpu/z80/z80.cpp
index 9e0fec6b487..7799dff84d5 100644
--- a/src/devices/cpu/z80/z80.cpp
+++ b/src/devices/cpu/z80/z80.cpp
@@ -3126,6 +3126,8 @@ OP(op,ff) { rst(0x38);
 
 void z80_device::take_nmi()
 {
+	PRVPC = 0xffff; // HACK: segag80r protection kludge
+
 	/* Check if processor was halted */
 	leave_halt();
 
@@ -3146,6 +3148,8 @@ void z80_device::take_interrupt()
 {
 	int irq_vector;
 
+	PRVPC = 0xffff; // HACK: segag80r protection kludge
+
 	/* Check if processor was halted */
 	leave_halt();
 
@@ -3230,6 +3234,8 @@ void z80_device::take_interrupt()
 
 void nsc800_device::take_interrupt_nsc800()
 {
+	PRVPC = 0xffff; // HACK: segag80r protection kludge
+
 	/* Check if processor was halted */
 	leave_halt();
 
diff --git a/src/mame/drivers/segag80r.cpp b/src/mame/drivers/segag80r.cpp
index f278a775a67..d374bc6d561 100644
--- a/src/mame/drivers/segag80r.cpp
+++ b/src/mame/drivers/segag80r.cpp
@@ -172,8 +172,8 @@ offs_t segag80r_state::decrypt_offset(address_space &space, offs_t offset)
 	if ((uint16_t)pc == 0xffff || space.read_byte(pc) != 0x32)
 		return offset;
 
-	/* fetch the low byte of the address and munge it */
-	return (offset & 0xff00) | (*m_decrypt)(pc, space.read_byte(pc + 1));
+	/* munge the low byte of the address */
+	return (offset & 0xff00) | (*m_decrypt)(pc, offset & 0xff);
 }
 
 WRITE8_MEMBER(segag80r_state::mainram_w)