diff --git a/aclocal.m4 b/aclocal.m4
index 99bfe9516..f44632fe2 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -223,8 +223,9 @@ AC_SUBST(strip_dynamic)
 # -------------
 AC_DEFUN([AX_C99_STRTOD],
 [# On MinGW we need to jump through hoops to get a C99 compliant strtod().
+ # mingw-w64 doesn't need this, and the 64-bit version doesn't support it.
 case "${host}" in
-    *-*-mingw*)
+    *-*-mingw32)
         LDFLAGS+=" -Wl,--undefined=___strtod,--wrap,strtod,--defsym,___wrap_strtod=___strtod"
         ;;
 esac