diff --git a/CHANGELOG.md b/CHANGELOG.md
index d4a55ed7..a89610cd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,7 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 - Errors and warnings from KiAuto now are printed as errors and warnings.
-- Schematic dependencies are sorted in the generated Makefiles
+- Schematic dependencies are sorted in the generated Makefiles.
+- Makefile variables KIBOT, DEBUG and LOGFILE can be defined from outside.
 
 ### Fixed
 - Problem when using E/DRC filters and the output dir didn't exist.
diff --git a/kibot/kiplot.py b/kibot/kiplot.py
index 499f0033..f4c40e05 100644
--- a/kibot/kiplot.py
+++ b/kibot/kiplot.py
@@ -446,17 +446,17 @@ def generate_makefile(makefile, cfg_file, outputs, kibot_sys=False):
         fname = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', 'src', 'kibot'))
         if kibot_sys or not os.path.isfile(fname):
             fname = 'kibot'
-        f.write('KIBOT={}\n'.format(fname))
+        f.write('KIBOT?={}\n'.format(fname))
         dbg = ''
         if GS.debug_level > 0:
             dbg = '-'+'v'*GS.debug_level
-        f.write('DEBUG={}\n'.format(dbg))
+        f.write('DEBUG?={}\n'.format(dbg))
         f.write('CONFIG={}\n'.format(cfg_file))
         f.write('SCH={}\n'.format(os.path.relpath(GS.sch_file)))
         f.write('PCB={}\n'.format(os.path.relpath(GS.pcb_file)))
         f.write('DEST={}\n'.format(os.path.relpath(GS.out_dir)))
         f.write('KIBOT_CMD=$(KIBOT) $(DEBUG) -c $(CONFIG) -e $(SCH) -b $(PCB) -d $(DEST)\n')
-        f.write('LOGFILE=kibot_error.log\n')
+        f.write('LOGFILE?=kibot_error.log\n')
         f.write('\n')
         # Configure all outputs
         GS.outputs = outputs