diff --git a/py/mkenv.mk b/py/mkenv.mk
index cb678e8e78..7e99f59c10 100644
--- a/py/mkenv.mk
+++ b/py/mkenv.mk
@@ -56,7 +56,7 @@ RM = rm
 RSYNC = rsync
 SED = sed
 # Linux has 'nproc', macOS has 'sysctl -n hw.logicalcpu', this is cross-platform
-NPROC = $(PYTHON) -c 'import multiprocessing as mp; print(mp.cpu_count())'
+NPROC = $(PYTHON3) -c 'import multiprocessing as mp; print(mp.cpu_count())'
 
 AS = $(CROSS_COMPILE)as
 CC = $(CROSS_COMPILE)gcc
@@ -72,7 +72,7 @@ CXX += -m32
 LD += -m32
 endif
 
-MAKE_FROZEN = $(PYTHON) $(TOP)/tools/make-frozen.py
+MAKE_FROZEN = $(PYTHON3) $(TOP)/tools/make-frozen.py
 MPY_CROSS = $(TOP)/mpy-cross/mpy-cross
 MPY_TOOL = $(PYTHON3) $(TOP)/tools/mpy-tool.py
 PREPROCESS_FROZEN_MODULES = PYTHONPATH=$(TOP)/tools/python-semver $(TOP)/tools/preprocess_frozen_modules.py