diff --git a/cpu.cpp b/cpu.cpp
index 8b23949..5bd16ef 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -1671,7 +1671,7 @@ void cpu::trap(uint16_t vector, const int new_ipl, const bool is_interrupt)
 
 	it_is_a_trap = true;
 
-	for(;;) {
+	do {
 		try {
 			processing_trap_depth++;
 
@@ -1722,7 +1722,6 @@ void cpu::trap(uint16_t vector, const int new_ipl, const bool is_interrupt)
 
 			// if we reach this point then the trap was processed without causing
 			// another trap
-			break;
 		}
 		catch(const int exception) {
 			DOLOG(debug, true, "trap during execution of trap (%d)", exception);
@@ -1730,6 +1729,7 @@ void cpu::trap(uint16_t vector, const int new_ipl, const bool is_interrupt)
 			setPSW(before_psw, false);
 		}
 	}
+	while(0);
 }
 
 cpu::operand_parameters cpu::addressing_to_string(const uint8_t mode_register, const uint16_t pc, const word_mode_t word_mode) const
diff --git a/cpu.h b/cpu.h
index e06f125..af35766 100644
--- a/cpu.h
+++ b/cpu.h
@@ -150,6 +150,7 @@ public:
 	void lowlevel_register_sp_set(const uint8_t set, const uint16_t value);
 	uint16_t lowlevel_register_get(const uint8_t set, const uint8_t reg);
 	void lowlevel_psw_set(const uint16_t value) { psw = value; }
+	uint16_t lowlevel_register_sp_get(const uint8_t nr) const { return sp[nr]; }
 
 	void setStackPointer(const int which, const uint16_t value) { assert(which >= 0 && which < 4); sp[which] = value; }
 	void setPC(const uint16_t value) { pc = value; }
diff --git a/main.cpp b/main.cpp
index bab238b..213d7f5 100644
--- a/main.cpp
+++ b/main.cpp
@@ -174,6 +174,19 @@ int run_cpu_validation(const std::string & filename)
 			}
 
 			// TODO check SP[]
+			{
+				json_t *a_sp = json_object_get(registers_after, "sp");
+				size_t array_size = json_array_size(a_sp);
+				assert(array_size == 4);
+				for(size_t i=0; i<array_size; i++) {
+					json_t *temp = json_array_get(a_sp, i);
+					uint16_t sp = c->lowlevel_register_sp_get(i);
+					if (json_integer_value(temp) != sp) {
+						DOLOG(warning, true, "SP[%d] register mismatch (is: %06o (%d), should be: %06o (%d))", i, sp, sp, json_integer_value(temp), json_integer_value(temp));
+						err = true;
+					}
+				}
+			}
 
 			{
 				json_t *a_psw = json_object_get(registers_after, "psw");