cursynth 1.5 build failure (AUR)

Making all in mopo
make[2]: Entering directory '/home/neuromancer85/.aur/yaourt-tmp-neuromancer85/aur-cursynth/src/cursynth-1.5/mopo'
Making all in src
make[3]: Entering directory '/home/neuromancer85/.aur/yaourt-tmp-neuromancer85/aur-cursynth/src/cursynth-1.5/mopo/src'
  CXX      delay.o
  CXX      filter.o
  CXX      envelope.o
  CXX      feedback.o
  CXX      linear_slope.o
  CXX      midi_lookup.o
  CXX      mono_panner.o
  CXX      operators.o
  CXX      oscillator.o
In file included from mono_panner.cpp:20:0:
wave.h: In static member function ‘static mopo::mopo_float mopo::Wave::whitenoise()’:
wave.h:245:28: error: ‘rand’ was not declared in this scope
         return (2.0 * rand()) / RAND_MAX - 1;
                            ^
wave.h:245:33: error: ‘RAND_MAX’ was not declared in this scope
         return (2.0 * rand()) / RAND_MAX - 1;
                                 ^
Makefile:382: recipe for target 'mono_panner.o' failed
make[3]: *** [mono_panner.o] Error 1
make[3]: *** Waiting for unfinished jobs....
In file included from oscillator.h:22:0,
                 from oscillator.cpp:17:
wave.h: In static member function ‘static mopo::mopo_float mopo::Wave::whitenoise()’:
wave.h:245:28: error: ‘rand’ was not declared in this scope
         return (2.0 * rand()) / RAND_MAX - 1;
                            ^
wave.h:245:33: error: ‘RAND_MAX’ was not declared in this scope
         return (2.0 * rand()) / RAND_MAX - 1;
                                 ^
Makefile:382: recipe for target 'oscillator.o' failed
make[3]: *** [oscillator.o] Error 1
make[3]: Leaving directory '/home/neuromancer85/.aur/yaourt-tmp-neuromancer85/aur-cursynth/src/cursynth-1.5/mopo/src'
Makefile:329: recipe for target 'all-recursive' failed
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory '/home/neuromancer85/.aur/yaourt-tmp-neuromancer85/aur-cursynth/src/cursynth-1.5/mopo'
Makefile:446: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/neuromancer85/.aur/yaourt-tmp-neuromancer85/aur-cursynth/src/cursynth-1.5'
Makefile:365: recipe for target 'all' failed
make: *** [all] Error 2