diff --git a/compiler/res/prog8lib/c64utils.p8 b/compiler/res/prog8lib/c64utils.p8
index ad343f150..0683919cd 100644
--- a/compiler/res/prog8lib/c64utils.p8
+++ b/compiler/res/prog8lib/c64utils.p8
@@ -102,7 +102,6 @@ asmsub  uword2bcd  (uword value @ AY) clobbers(A,Y)  {
 		pla             ; read status register
 		and  #%00000100
 		sta  _had_irqd
-		sei				; disable interrupts because of bcd math
 		sed				; switch to decimal mode
 		lda  #0				; ensure the result is clear
 		sta  bcdbuff+0
@@ -341,6 +340,7 @@ _irq_handler_init
 		dex
 		dex
 		dex
+		cld
 		rts
 
 _irq_handler_end
diff --git a/sim65/src/components/Cpu6502.kt b/sim65/src/components/Cpu6502.kt
index 36196d08f..8143e6f94 100644
--- a/sim65/src/components/Cpu6502.kt
+++ b/sim65/src/components/Cpu6502.kt
@@ -702,13 +702,12 @@ class Cpu6502(private val illegalInstrsAllowed: Boolean) : BusComponent(), ICpu
             var lo = (A and 0x0f) + (operand and 0x0f) + if (Status.C) 1 else 0
             if (lo and 0xff > 9) lo += 6
             var hi = (A shr 4) + (operand shr 4) + if (lo > 15) 1 else 0
+            Status.N = (hi and 8) != 0      // strange... other sources say "BCD is never negative on NMOS 6502 (bug)"
+            Status.V = ((((hi shl 4) xor A) and 0x80) !=0) && ((A xor operand) and 0x80)==0   // strange... other sources say "V is never set in BCD mode"
             if (hi and 0xff > 9) hi += 6
-            val result = lo and 0x0f or (hi shl 4)
-            A = result and 0xff
+            A = lo and 0x0f or (hi shl 4) and 0xff
             Status.C = hi > 15
             Status.Z = A == 0
-            Status.V = false  // BCD never sets overflow flag
-            Status.N = false  // BCD is never negative on NMOS 6502 (bug)
         } else {
             // normal add
             val result = A + operand + if (Status.C) 1 else 0
@@ -990,21 +989,22 @@ class Cpu6502(private val illegalInstrsAllowed: Boolean) : BusComponent(), ICpu
     }
 
     private fun iSbc() {
-        val operand = getFetched()
         if (Status.D) {
-            var lo = (A and 0x0f) - (operand and 0x0f) - if (Status.C) 0 else 1
+            val operand = getFetched()
+            var lo: Int
+            var hi: Int
+            lo = (A and 0x0f) - (operand and 0x0f) - if (Status.C) 0 else 1
             if (lo and 0x10 != 0) lo -= 6
-            var hi = (A shr 4) - (operand shr 4) - if (lo and 0x10 != 0) 1 else 0
+            hi = (A shr 4) - (operand shr 4) - if (lo and 0x10 != 0) 1 else 0
             if (hi and 0x10 != 0) hi -= 6
-            val result = lo and 0x0f or ((hi shl 4) and 0xff)
-            Status.C = hi and 255 < 15
-            Status.Z = result == 0
-            Status.V = false // BCD never sets overflow flag
-            Status.N = false // BCD is never negative on NMOS 6502 (bug)
-            A = result and 255
+            A = lo and 0x0f or (hi shl 4) and 0xff
+            Status.C = hi and 0xff < 15
+            Status.V = false  // BCD never sets overflow flag
+            Status.Z = A==0
+            Status.N = (A and 0b10000000) != 0
         } else {
             // normal sub
-            val invertedOperand = operand xor 255
+            val invertedOperand = getFetched() xor 255
             val result = A + invertedOperand + if (Status.C) 1 else 0
             Status.C = result > 255
             Status.V = (A xor invertedOperand) and (A xor result) and 0x0080 != 0
diff --git a/sim65/test/TestCommon6502.kt b/sim65/test/TestCommon6502.kt
index fcd1b96a6..850cf1bac 100644
--- a/sim65/test/TestCommon6502.kt
+++ b/sim65/test/TestCommon6502.kt
@@ -505,11 +505,10 @@ abstract class TestCommon6502 {
         mpu.step()
         assertEquals(0x0002, mpu.PC)
         assertEquals(0x80, mpu.A)
-        assertTrue(mpu.Status.N)
-        assertTrue(mpu.Status.V)
-        assertFalse(mpu.Status.Z)
         assertFalse(mpu.Status.C)
-
+        assertFalse(mpu.Status.Z)
+        assertTrue(mpu.Status.V)
+        assertTrue(mpu.Status.N)
     }
 
     @Test
@@ -547,14 +546,13 @@ abstract class TestCommon6502 {
         assertEquals(0x0004, mpu.PC)
         assertEquals(0x93, mpu.A)
         assertFalse(mpu.Status.N)
-        assertTrue(mpu.Status.V)
         assertFalse(mpu.Status.Z)
         assertTrue(mpu.Status.C)
-
-        // ADC Absolute, X-Indexed
-
+        assertTrue(mpu.Status.V)
     }
 
+    // ADC Absolute, X-Indexed
+
     @Test
     fun test_adc_bcd_off_abs_x_carry_clear_in_accumulator_zeroes() {
 
@@ -5696,10 +5694,10 @@ abstract class TestCommon6502 {
         mpu.step()
         assertEquals(0x0002, mpu.PC)
         assertEquals(0x9a, mpu.A)
-        assertTrue(mpu.Status.N)
-        assertFalse(mpu.Status.V)
         assertFalse(mpu.Status.Z)
         assertTrue(mpu.Status.C)
+        assertFalse(mpu.Status.V)
+        assertTrue(mpu.Status.N)
     }
 
     @Test
@@ -5715,17 +5713,18 @@ abstract class TestCommon6502 {
         mpu.step()
         assertEquals(0x0002, mpu.PC)
         assertEquals(0x99, mpu.A)
-        assertTrue(mpu.Status.N)
-        assertFalse(mpu.Status.V)
         assertFalse(mpu.Status.Z)
         assertFalse(mpu.Status.C)
+        assertFalse(mpu.Status.V)
+        assertTrue(mpu.Status.N)
     }
 
     @Test
     fun test_sbc_bcd_on_immediate_20_minus_0a_carry_unset() {
         mpu.Status.D = true
+        mpu.Status.C = false
         mpu.A = 0x20
-        // $0000 SBC #$00
+        // $0000 SBC #$0a
         writeMem(memory, 0x0000, listOf(0xe9, 0x0a))
         mpu.step()
         assertEquals(0x0002, mpu.PC)