diff --git a/m4/manywarnings.m4 b/m4/manywarnings.m4
index 18249b8f2..eaa145c96 100644
--- a/m4/manywarnings.m4
+++ b/m4/manywarnings.m4
@@ -327,3 +327,10 @@ m4_defun([gl_MANYWARN_ALL_GCC(C++)],
 [
   gl_MANYWARN_ALL_GCC_CXX_IMPL([$1])
 ])
+
+# Specialization for _AC_LANG = Objective C.
+# Use of m4_defun rather than AC_DEFUN works around a bug in autoconf < 2.63b.
+m4_defun([gl_MANYWARN_ALL_GCC(Objective C)],
+[
+  gl_MANYWARN_ALL_GCC_OBJC_IMPL([$1])
+])