As of mbed-os 6.0, printf does not print floating point values

I upgraded to mbed-os 6.13.0. Now, printf does not print floating point values. Here is an example fragment of printf output: "accel = %13.7f". The "%13.7f" is displayed instead of accel's value.

This phenomenon also happens in the "blinky" example that also uses mbe-os 6.13.0

The link

https://github.com/ARMmbed/mbed-os/blob/master/platform/source/minimal-printf/README.md 

explains that this change was made as of Mbed OS 6.0. A solution is given consisting of an addition to mbed_app.json. However, I can't find that file anywhere in the blinky file collection.

In the blinky file collection, under "BUILD/LPC1768/ARMC6" is a file called mbed_config.h. Within that file is

#define MBED_CONF_PLATFORM_MINIMAL_PRINTF_ENABLE_FLOATING_POINT 0

Changing its value to "1" doesn't help.

A solution to this mystery would be greatly appreciated. Thanks!