diff --git a/m4/python.m4 b/m4/python.m4
index a1396df..e1c5266 100644
--- a/m4/python.m4
+++ b/m4/python.m4
@@ -1,7 +1,7 @@
 ## this one is commonly used with AM_PATH_PYTHONDIR ...
 dnl AM_CHECK_PYMOD(MODNAME [,SYMBOL [,ACTION-IF-FOUND [,ACTION-IF-NOT-FOUND]]])
 dnl Check if a module containing a given symbol is visible to python.
-AC_DEFUN(AM_CHECK_PYMOD,
+AC_DEFUN([AM_CHECK_PYMOD],
 [AC_REQUIRE([AM_PATH_PYTHON])
 py_mod_var=`echo $1['_']$2 | sed 'y%./+-%__p_%'`
 AC_MSG_CHECKING(for ifelse([$2],[],,[$2 in ])python module $1)