diff --git a/bus.cpp b/bus.cpp
index 03ab696..f969719 100644
--- a/bus.cpp
+++ b/bus.cpp
@@ -285,10 +285,7 @@ uint16_t bus::read(const uint16_t a, const bool word_mode, const bool use_prev,
 
 	int run_mode = (c->getPSW() >> (use_prev ? 12 : 14)) & 3;
 
-//	if (run_mode == 1 && is_11_34)
-//		run_mode = 3;
-
-	uint32_t m_offset = calculate_physical_address(run_mode, a, !peek_only, false, peek_only);
+	uint32_t m_offset = calculate_physical_address(run_mode, a, !peek_only, false, peek_only, word_mode);
 
 	if (word_mode)
 		temp = m -> readByte(m_offset);
@@ -339,12 +336,13 @@ void bus::setMMR2(const uint16_t value)
 	MMR2 = value;
 }
 
-uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, const bool trap_on_failure, const bool is_write, const bool peek_only)
+uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, const bool trap_on_failure, const bool is_write, const bool peek_only, const bool word_mode)
 {
 	uint32_t m_offset = 0;
 
+	const uint8_t apf = a >> 13; // active page field
+
 	if (MMR0 & 1) {
-		const uint8_t apf = a >> 13; // active page field
 
 		// TODO: D/I
 		m_offset = pages[run_mode][0][apf].par * 64;  // memory offset  TODO: handle 16b int-s
@@ -466,6 +464,16 @@ uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, c
 		m_offset = a;
 	}
 
+	if ((m_offset & 1) && word_mode == 0 && peek_only == false) {
+		DOLOG(debug, !peek_only, "bus::calculate_physical_address::m_offset %o", m_offset);
+		DOLOG(debug, true, "TRAP(004) (throw 5) on address %06o", a);
+		c->schedule_trap(004);  // invalid access
+
+		pages[run_mode][0][apf].pdr |= 1 << 7;  // TODO: D/I
+
+		throw 5;
+	}
+
 	return m_offset;
 }
 
@@ -787,7 +795,7 @@ void bus::write(const uint16_t a, const bool word_mode, uint16_t value, const bo
 		return;
 	}
 
-	uint32_t m_offset = calculate_physical_address(run_mode, a, true, true, false);
+	uint32_t m_offset = calculate_physical_address(run_mode, a, true, true, false, word_mode);
 
 	DOLOG(debug, true, "WRITE to %06o/%07o: %o", a, m_offset, value);
 
diff --git a/bus.h b/bus.h
index b4c92d5..9b8cdd6 100644
--- a/bus.h
+++ b/bus.h
@@ -90,5 +90,5 @@ public:
 
 	uint16_t get_switch_register() const { return switch_register; }
 
-	uint32_t calculate_physical_address(const int run_mode, const uint16_t a, const bool trap_on_failure, const bool is_write, const bool peek_only);
+	uint32_t calculate_physical_address(const int run_mode, const uint16_t a, const bool trap_on_failure, const bool is_write, const bool peek_only, const bool word_mode);
 };
diff --git a/console_ncurses.cpp b/console_ncurses.cpp
index a90b7b6..6a3555b 100644
--- a/console_ncurses.cpp
+++ b/console_ncurses.cpp
@@ -139,7 +139,7 @@ void console_ncurses::panel_update_thread()
 		int      run_mode      = current_PSW >> 14;
 
 		uint16_t current_PC    = c->getPC();
-		uint32_t full_addr     = b->calculate_physical_address(run_mode, current_PC, false, false, true);
+		uint32_t full_addr     = b->calculate_physical_address(run_mode, current_PC, false, false, true, true);
 
 		uint16_t current_instr = b->readWord(current_PC);
 
diff --git a/cpu.cpp b/cpu.cpp
index 748d9b7..6d2c55b 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -1657,7 +1657,7 @@ void cpu::trap(const uint16_t vector, const int new_ipl, const bool is_interrupt
 	// make sure the trap vector is retrieved from kernel space
 	psw &= 037777;  // mask off 14/15
 
-	if ((b->getMMR0() & 0160000) == 0) {
+	if ((b->getMMR0() & 0160000) == 0 && vector != 4) {
 		b->setMMR2(vector);
 		b->addToMMR1(-2, 6);
 		b->addToMMR1(-2, 6);
@@ -2161,7 +2161,12 @@ void cpu::step_a()
 		b->clearMMR1();
 
 	if (scheduled_trap) {
-		trap(scheduled_trap, 7, true);
+		try {
+			trap(scheduled_trap, 7, true);
+		}
+		catch(const int exception) {
+			DOLOG(debug, true, "2nd-bus-trap during execution of command (%d)", exception);
+		}
 
 		scheduled_trap = 0;