diff --git a/configure.ac b/configure.ac
index 76a0ecf9..289b2995 100644
--- a/configure.ac
+++ b/configure.ac
@@ -133,6 +133,8 @@ if test "$enable_gcc_warnings" = yes; then
   # Warnings for the test suite only.
   gl_WARN_ADD([-Wundef], [WARN_CXXFLAGS_TEST])
   gl_WARN_ADD([-pedantic], [WARN_CXXFLAGS_TEST])
+  # Clang++ 3.2+ reject C code generated by Flex.
+  gl_WARN_ADD([-Wno-null-conversion], [WARN_NO_NULL_CONVERSION_CXXFLAGS])
   # Variants break strict aliasing analysis.
   gl_WARN_ADD([-fno-strict-aliasing], [NO_STRICT_ALIAS_CXXFLAGS])
   CXXFLAGS=$save_CXXFLAGS
diff --git a/examples/calc++/local.mk b/examples/calc++/local.mk
index c0cb5e81..6eb31f89 100644
--- a/examples/calc++/local.mk
+++ b/examples/calc++/local.mk
@@ -69,5 +69,7 @@ nodist_examples_calc___calc___SOURCES =		\
   $(calc_sources)
 
 examples_calc___calc___CPPFLAGS = -I$(top_builddir)/examples/calc++
+examples_calc___calc___CXXFLAGS =			\
+  $(AM_CXXFLAGS) $(WARN_NO_NULL_CONVERSION_CXXFLAGS)
 dist_TESTS += examples/calc++/calc++.test
 endif