diff --git a/python/Makefile.am b/python/Makefile.am
index a254480f9..13618dc2f 100644
--- a/python/Makefile.am
+++ b/python/Makefile.am
@@ -29,12 +29,12 @@ pkglibexecpython_DATA += stap-resolve-module-function.py
 
 all-local:
 if HAVE_PYTHON2_PROBES
-	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON) setup.py build \
+	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON) setup.py build \
          --build-base $(shell readlink -f $(builddir))/py2build \
          --verbose)
 endif
 if HAVE_PYTHON3_PROBES
-	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
+	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
          --build-base $(shell readlink -f $(builddir))/py3build \
          --verbose)
 endif
@@ -45,7 +45,7 @@ endif
 # and we need to keep separate build directories for python 2 and 3.
 install-exec-local:
 if HAVE_PYTHON2_PROBES
-	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON) setup.py build \
+	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON) setup.py build \
          --build-base $(shell readlink -f $(builddir))/py2build \
 	 install --prefix $(DESTDIR)$(prefix) \
 	 --single-version-externally-managed \
@@ -53,7 +53,7 @@ if HAVE_PYTHON2_PROBES
          --verbose)
 endif
 if HAVE_PYTHON3_PROBES
-	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
+	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
          --build-base $(shell readlink -f $(builddir))/py3build \
 	 install --prefix $(DESTDIR)$(prefix) \
 	 --single-version-externally-managed \
diff --git a/python/Makefile.in b/python/Makefile.in
index 1216eefff..62fe2129c 100644
--- a/python/Makefile.in
+++ b/python/Makefile.in
@@ -624,10 +624,10 @@ uninstall-am: uninstall-pkglibexecpythonDATA \
 
 
 @HAVE_PYTHON_PROBES_TRUE@all-local:
-@HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON) setup.py build \
+@HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON) setup.py build \
 @HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@         --build-base $(shell readlink -f $(builddir))/py2build \
 @HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@         --verbose)
-@HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
+@HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
 @HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@         --build-base $(shell readlink -f $(builddir))/py3build \
 @HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@         --verbose)
 
@@ -635,13 +635,13 @@ uninstall-am: uninstall-pkglibexecpythonDATA \
 # since only the build command has the '--build-base' directory option
 # and we need to keep separate build directories for python 2 and 3.
 @HAVE_PYTHON_PROBES_TRUE@install-exec-local:
-@HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON) setup.py build \
+@HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON) setup.py build \
 @HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@         --build-base $(shell readlink -f $(builddir))/py2build \
 @HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	 install --prefix $(DESTDIR)$(prefix) \
 @HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	 --single-version-externally-managed \
 @HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	 --record $(shell readlink -f $(builddir))/py2build/install_files.txt \
 @HAVE_PYTHON2_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@         --verbose)
-@HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
+@HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	(cd $(srcdir); CFLAGS="$(CFLAGS) $(AM_CPPFLAGS)" $(PYTHON3) setup.py build \
 @HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@         --build-base $(shell readlink -f $(builddir))/py3build \
 @HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	 install --prefix $(DESTDIR)$(prefix) \
 @HAVE_PYTHON3_PROBES_TRUE@@HAVE_PYTHON_PROBES_TRUE@	 --single-version-externally-managed \