'Invalid parameter specified' on prepared query with a double

'Invalid parameter specified' on prepared query with a double

In our project we get an Exception: 'Invalid parameters specified'. We've determined that this is specifically when we use a double variable.

In the scenarios below the first two instances of TPgQuery are executing properly, however on opening the third query, we get the the error.

procedure TMyForm.OkButtonClick(Sender: TObject);
var
objQuery: TPgQuery;
dblValue: Double;
begin
objQuery := TPgQuery.Create(nil);
try
    objQuery.Connection := DATACON;
    objQuery.SQL.Text := 'SELECT :dblValue';
    objQuery.ParamByName('dblValue').Value := 13.37;
    objQuery.Open(); // OK
finally
    objQuery.Free;
end;

DATACON.ExecSQL('PREPARE PreparedQuery(double precision) AS SELECT $1');

objQuery := TPgQuery.Create(nil);
try
    objQuery.Connection := DATACON;
    objQuery.SQL.Text := 'EXECUTE PreparedQuery(:dblValue)';
    objQuery.ParamByName('dblValue').Value := 1.23;
    objQuery.Open(); // OK
finally
    objQuery.Free;
end;

dblValue := 1.23;
objQuery := TPgQuery.Create(nil);
try
    objQuery.Connection := DATACON;
    objQuery.SQL.Text := 'EXECUTE PreparedQuery(:dblValue)';
    objQuery.ParamByName('dblValue').Value := dblValue;
    objQuery.Open(); // Returns error
finally
    objQuery.Free;
end;
end;

This test scenario is independent of the database used. We also tried setting the DataType property to ftFloat, this does not make a difference.

We use PgDac Professional Edition 7.4.0 using RAD Studio 11.2.

We've previously used PgDac 7.2.1 on RAD Studio 11 and this does not return any error with these scenarios.