diff --git a/README.md b/README.md
index 4002db1..28467a6 100644
--- a/README.md
+++ b/README.md
@@ -138,7 +138,7 @@ Only valid on SDL mode
   -saturnCardSlot int
         slot for the 256kb Saturn card. -1 for none (default -1)
   -thunderClockCardSlot int
-        slot for the ThunderClock Plus card. -1 for none (default 5)
+        slot for the ThunderClock Plus card. -1 for none (default 4)
   -traceCpu
         dump to the console the CPU execution. Use F11 to toggle.
   -traceSS
diff --git a/apple2main.go b/apple2main.go
index 59b22cf..2f5631f 100644
--- a/apple2main.go
+++ b/apple2main.go
@@ -49,7 +49,7 @@ func MainApple() *Apple2 {
 		"slot for the 256kb Saturn card. -1 for none")
 	thunderClockCardSlot := flag.Int(
 		"thunderClockCardSlot",
-		5,
+		4,
 		"slot for the ThunderClock Plus card. -1 for none")
 	mono := flag.Bool(
 		"mono",