GCC compiler unable to understand c++11

I am trying to compile a c++ program in Qt Creator under OpenSuse 15.0. Currently I get the following error:

'round' is not a member of 'std'

I know this is an error caused by my compiler using a pre-c++11 standart. However in my .pro file I specified:

CONFIG += c++11 console

According to g++ --version I have the following compiler installed

g++ (SUSE Linux) 7.3.1 20180323 [gcc-7-branch revision 258812]

Any idea why my compiler is still unable to understand c++11 standards?