if statement fails when used with semi-colon separator

I don't understand why I'm having an error with Python when I use a single-line if statement after a semicolon (used as separator).

This is ok:

if True: print("it works")
#### it works

But this gives a syntax error:

a=1; if True: print("it should work?")
#### SyntaxError: invalid syntax

I use Python3, with Spyder.

Thanks for any explanation!