diff --git a/aclocal.m4 b/aclocal.m4
index a47eba42c..1b2dd6a1e 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -23,11 +23,13 @@ AC_SUBST(install_suffix)
 # ------------------------------
 # Sub-macro for AX_C_UNDERSCORES_LEADING and AX_C_UNDERSCORES_TRAILING.
 # Unwarranted assumptions:
-#   - the object file produced by AC_COMPILE_IFELSE is called "conftest.$ac_objext"
-#   - the nm(1) utility is available, and its name is "nm".
+#   - the object file produced by AC_COMPILE_IFELSE is called
+#     "conftest.$ac_objext"
+#   - the nm(1) utility or an equivalent is available, and its name
+#     is defined by the $NM variable.
 AC_DEFUN([_AX_C_UNDERSCORES_MATCH_IF],
 [AC_COMPILE_IFELSE([AC_LANG_SOURCE([void underscore(void){}])],
-[AS_IF([nm conftest.$ac_objext|grep $1 >/dev/null 2>/dev/null],[$2],[$3])],
+[AS_IF([$NM conftest.$ac_objext|grep $1 >/dev/null 2>/dev/null],[$2],[$3])],
 [AC_MSG_ERROR([underscore test crashed])]
 )])