diff --git a/bus.cpp b/bus.cpp
index d00d7dd..4030e18 100644
--- a/bus.cpp
+++ b/bus.cpp
@@ -312,6 +312,11 @@ uint16_t bus::read(const uint16_t a, const bool word_mode, const bool use_prev)
 
 	m_offset += a & 8191;
 
+	if (m_offset >= n_pages * 8192) {
+		D(fprintf(stderr, "bus::read %o >= %o\n", m_offset, n_pages * 8192);)
+		c->schedule_trap(04);  // invalid address
+	}
+
 	if (word_mode)
 		temp = m -> readByte(m_offset);
 	else
@@ -575,6 +580,11 @@ uint16_t bus::write(const uint16_t a, const bool word_mode, uint16_t value, cons
 
 	m_offset += a & 8191;
 
+	if (m_offset >= n_pages * 8192) {
+		D(fprintf(stderr, "bus::write %o >= %o\n", m_offset, n_pages * 8192);)
+		c->schedule_trap(04);  // invalid address
+	}
+
 	if (word_mode)
 		m->writeByte(m_offset, value);
 	else
diff --git a/cpu.cpp b/cpu.cpp
index 121fa61..8cb2edb 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -1187,6 +1187,11 @@ void cpu::busError()
 	trap(4);
 }
 
+void cpu::schedule_trap(const uint16_t vector)
+{
+	scheduled_trap = vector;
+}
+
 void cpu::trap(const uint16_t vector, const int new_ipl)
 {
 	uint16_t before_psw = getPSW();
@@ -1605,6 +1610,12 @@ void cpu::step()
 {
 	check_queued_interrupts();
 
+	if (scheduled_trap) {
+		trap(scheduled_trap, 7);
+
+		scheduled_trap = 0;
+	}
+
 	uint16_t temp_pc = getPC();
 
 	if (temp_pc & 1)
diff --git a/cpu.h b/cpu.h
index 049ab32..5663cb6 100644
--- a/cpu.h
+++ b/cpu.h
@@ -19,6 +19,7 @@ private:
 	uint16_t psw   { 0 };
 	uint16_t fpsr  { 0 };
 	uint16_t stackLimitRegister { 0 };
+	uint8_t  scheduled_trap     { 0 };
 	bool runMode     { false };
 	bool emulateMFPT { false };
 
@@ -68,6 +69,7 @@ public:
 
 	void busError();
 	void trap(const uint16_t vector, const int new_ipl = -1);
+	void schedule_trap(const uint16_t vector);
 
 	void setEmulateMFPT(const bool v) { emulateMFPT = v; }