Exeption decoder for ESP8266 from ArduinoIDE does not find decoder info in the firmware.elf

I moved one of my projects from the arduino IDE to platformio. After some rework, it works perfect, but my project with ESP8266 has about one exception per day. Therefore I used the exception decoder from the arduinoIDE but the decoder does not find the necessary info witch lines of code were used before the exception.
To test the exeption handling I used the library ESPsaveCrash. If I compile this example in arduino IDE, the exeption decoder shows the last used lines of code before crash as expected. The same done in platformio the decoder does not find the info in the firmware.elf file.
In platform.ini I used:
build_unflags = -fno-exceptions
build_flags = -fexceptions
But it does not work, has anyone an idea how I can solve the problem?

Found by myself:
build_type = debug
is necessary, then it works