--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -22,7 +22,8 @@
 
 MODBUILT_NAMES=    _MODBUILT_NAMES_
 MODDISABLED_NAMES= _MODDISABLED_NAMES_
-MODOBJS=           _MODOBJS_
+# filter out duplicate object files (_math.o)
+MODOBJS=           $(sort _MODOBJS_)
 MODLIBS=           _MODLIBS_
 
 # === Variables set by configure
@@ -602,8 +603,9 @@ pybuilddir.txt: $(BUILDPYTHON)
 	fi
 
 # This is shared by the math and cmath modules
+# don't build with -fPIC when building as math and cmath as builtins
 Modules/_math.o: Modules/_math.c Modules/_math.h
-	$(CC) -c $(CCSHARED) $(PY_CORE_CFLAGS) -o $@ $<
+	$(CC) -c $(if $(findstring _math.o, $(MODOBJS)),,$(CCSHARED)) $(PY_CORE_CFLAGS) -o $@ $<
 
 # blake2s is auto-generated from blake2b
 $(srcdir)/Modules/_blake2/blake2s_impl.c: $(srcdir)/Modules/_blake2/blake2b_impl.c $(srcdir)/Modules/_blake2/blake2b2s.py