Generated files not regenerated when the generator changes

I have a bunch of files generated by a python script. When changing the gputop-oa-codegen.py script, files don't get regenerated. Is this expected?

oa_generator = generator(                                                          
  prog_python2,                                                                    
  arguments : ['@CURRENT_SOURCE_DIR@/../scripts/gputop-oa-codegen.py', '@INPUT@',  
               '--chipset', '@EXTRA_ARGS@', '--code', '@OUTPUT0@',                 
               '--header', '@OUTPUT1@'],                                           
  output : ['@BASENAME@.c', '@BASENAME@.h'],                                       
)                                                                                  
                                                                                   
oa_sources = []                                                                    
foreach hw : ['hsw', 'bdw', 'chv', 'sklgt2', 'sklgt3', 'sklgt4', 'bxt',            
              'kblgt2', 'kblgt3', 'glk', 'cflgt2', 'cflgt3', 'cnl']                
  _xml = '../gputop-data/oa-@0@.xml'.format(hw)                                    
  oa_sources += oa_generator.process(_xml, extra_args : hw)                        
endforeach                                                                         
                                                                                   
gputop_client_oa = static_library('gputop_client_oa', oa_sources,                              
                                  c_args : ['-Wno-unused-parameter', '-Wno-unused-function'],  
                                  dependencies : mesa_dep)