diff --git a/configure.in b/configure.in
index 19339dc6..ea5c1253 100644
--- a/configure.in
+++ b/configure.in
@@ -22,7 +22,7 @@ AC_PROG_MAKE_SET
 AC_PROG_AWK
 
 AC_FUNC_GETLOADAVG(plugins)
-ifdef(AC_FUNC_STRTOD,AC_FUNC_STRTOD,AM_FUNC_STRTOD)
+ifdef([AC_FUNC_STRTOD],[AC_FUNC_STRTOD],[AM_FUNC_STRTOD])
 dnl AM_WITH_REGEX
 AC_PROG_RANLIB