./core/ikwiad -d 'GFa -> FG b ' raise assertion failed

Starting parse
Entering state 0
Reading a token: Next token is token "LTL start marker" (1.1: )
Shifting token "LTL start marker" (1.1: )
Entering state 1
Reading a token: Next token is token "always operator" (1.1: )
Shifting token "always operator" (1.1: )
Entering state 13
Reading a token: Next token is token "sometimes operator" (1.2: )
Shifting token "sometimes operator" (1.2: )
Entering state 12
Reading a token: Next token is token "atomic proposition" (1.3: a)
Shifting token "atomic proposition" (1.3: a)
Entering state 16
Reading a token: Next token is token "implication operator" (1.5-6: )
Reducing stack by rule 53 (line 404):
   $1 = token "atomic proposition" (1.3: a)
-> $$ = nterm booleanatom (1.3: a)
Stack now 12 13 1 0
Entering state 22
Reducing stack by rule 125 (line 825):
   $1 = nterm booleanatom (1.3: Assertion failed: (i != m.ap2name.end()), function ap_name, file formula.cc, line 1016.
Abort trap: 6