diff --git a/src/ifcopenshell-python/Makefile b/src/ifcopenshell-python/Makefile
index 11fa50887e..b814cb3163 100644
--- a/src/ifcopenshell-python/Makefile
+++ b/src/ifcopenshell-python/Makefile
@@ -27,26 +27,15 @@ SED:=sed -i '' -e
 endif
 endif
 
-# TODO: we should simplify this at some point...
-ifeq ($(PYVERSION), py310)
-PYNUMBER:=310
-endif
-ifeq ($(PYVERSION), py311)
-PYNUMBER:=311
-endif
-ifeq ($(PYVERSION), py312)
-PYNUMBER:=312
-endif
-ifeq ($(PYVERSION), py313)
-PYNUMBER:=313
-endif
-ifeq ($(PYVERSION), py314)
-PYNUMBER:=314
-endif
-ifndef PYNUMBER
-$(error Unsupported PYVERSION '$(PYVERSION)')
+SUPPORTED_PYVERSIONS := py310 py311 py312 py313 py314
+
+ifeq ($(filter $(PYVERSION),$(SUPPORTED_PYVERSIONS)),)
+$(error Unsupported PYVERSION=$(PYVERSION). Must be one of $(SUPPORTED_PYVERSIONS))
 endif
 
+PYMINOR:=$(subst py3,,$(PYVERSION))
+PYNUMBER:=3$(PYMINOR)
+
 # We actually do support glibc 2.28-2.30 (see #5636)
 # but those are old and there's no demand for it.
 ifeq ($(PLATFORM), linux64)