diff --git a/lemon/assert.h b/lemon/assert.h
--- a/lemon/assert.h
+++ b/lemon/assert.h
@@ -107,8 +107,10 @@
 #    define LEMON_FUNCTION_NAME (__PRETTY_FUNCTION__)
 #  elif defined _MSC_VER
 #    define LEMON_FUNCTION_NAME (__FUNCSIG__)
+#  elif __STDC_VERSION__ >= 199901L
+#    define LEMON_FUNCTION_NAME (__func__)
 #  else
-#    define LEMON_FUNCTION_NAME (__func__)
+#    define LEMON_FUNCTION_NAME ("<unknown>")
 #  endif
 #endif