Index: subversion/libsvn_ra_serf/options.c
===================================================================
--- subversion/libsvn_ra_serf/options.c	(revision 1823355)
+++ subversion/libsvn_ra_serf/options.c	(working copy)
@@ -71,6 +71,9 @@
   svn_ra_serf__response_handler_t inner_handler;
   void *inner_baton;
 
+  /* Have we received any DAV headers at all? */
+  svn_boolean_t dav_header_received;
+
   const char *activity_collection;
   svn_revnum_t youngest_rev;
 
@@ -165,6 +168,8 @@
       apr_array_header_t *vals = svn_cstring_split(val, ",", TRUE,
                                                    opt_ctx->pool);
 
+      opt_ctx->dav_header_received = TRUE;
+
       /* Right now we only have a few capabilities to detect, so just
          seek for them directly.  This could be written slightly more
          efficiently, but that wouldn't be worth it until we have many
@@ -396,6 +401,14 @@
       serf_bucket_headers_do(hdrs, capabilities_headers_iterator_callback,
                              opt_ctx);
 
+      /* Bail out early if we're not talking to a DAV server. */
+      if (!opt_ctx->dav_header_received)
+        {
+          return svn_error_create(
+              SVN_ERR_RA_DAV_OPTIONS_REQ_FAILED, NULL,
+              _("The server does not support the HTTP/DAV protocol"));
+        }
+
       /* Assume mergeinfo capability unsupported, if didn't receive information
          about server or repository mergeinfo capability. */
       if (!svn_hash_gets(session->capabilities, SVN_RA_CAPABILITY_MERGEINFO))