diff --git a/bus.cpp b/bus.cpp
index 315c070..7a65cb1 100644
--- a/bus.cpp
+++ b/bus.cpp
@@ -407,6 +407,8 @@ uint16_t bus::write(const uint16_t a, const bool word_mode, uint16_t value, cons
 				DOLOG(debug, true, "writeb PSW %s", a & 1 ? "MSB" : "LSB");
 				uint16_t vtemp = c -> getPSW();
 
+				value &= ~16;  // cannot set T bit via this
+
 				if (a & 1)
 					vtemp = (vtemp & 0x00ff) | (value << 8);
 				else
@@ -433,7 +435,7 @@ uint16_t bus::write(const uint16_t a, const bool word_mode, uint16_t value, cons
 		else {
 			if (a == 0177776) { // PSW
 				DOLOG(debug, true, "write PSW %o", value);
-				c -> setPSW(value, false);
+				c -> setPSW(value & ~16, false);
 				return value;
 			}
 
diff --git a/cpu.cpp b/cpu.cpp
index 9680a5b..e596d41 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -1366,9 +1366,9 @@ bool cpu::single_operand_instructions(const uint16_t instr)
 		case 0b000110111: // MFPS (get PSW to something) / SXT
 				 if (word_mode) {  // MFPS
 					 uint16_t temp      = psw & 0xff;
-					 bool     extend_b7 = temp & 128;
+					 bool     extend_b7 = psw & 128;
 
-					 if (extend_b7)
+					 if (extend_b7 && dst_mode == 0)
 						 temp |= 0xff00;
 
 					 set_flags = putGAM(dst_mode, dst_reg, word_mode, temp, false);
@@ -1376,7 +1376,7 @@ bool cpu::single_operand_instructions(const uint16_t instr)
 					 if (set_flags) {
 						 setPSW_z(temp == 0);
 						 setPSW_v(false);
-						 setPSW_n(!extend_b7);
+						 setPSW_n(extend_b7);
 					 }
 				 }
 				 else {  // SXT