diff --git a/m4/reentrant.m4 b/m4/reentrant.m4
index b7e9a345..29cc809e 100644
--- a/m4/reentrant.m4
+++ b/m4/reentrant.m4
@@ -351,7 +351,7 @@ dnl and that in turn setup.h will define _REENTRANT.
 dnl Internal macro for CARES_CONFIGURE_REENTRANT.
 
 AC_DEFUN([CARES_CONFIGURE_FROM_NOW_ON_WITH_REENTRANT], [
-AC_DEFINE(NEED_REENTRANT, 1,
+AC_DEFINE([NEED_REENTRANT], [1],
   [Define to 1 if _REENTRANT preprocessor symbol must be defined.])
 cat >>confdefs.h <<_ACEOF
 #ifndef _REENTRANT