PLOT OVER 1; causes an error warning

[Tailzer]

if you add the OVER 1 command to PLOT followed by semicolon it causes the extension to think there is an error?
This is the code that created the error.
5 LET x=0
10 LET t=0.1
20 IF INKEY$="p" THEN GO TO 35
30 GO TO 10
35 LET x0=x
40 LET x=x+t
45 IF x>=255 THEN LET x=0
50 PLOT OVER 1;x0,0: PLOT x,0
55 LET t=t+.2
60 GO TO 20