diff --git a/remote-curl.c b/remote-curl.c
index d388120..256326a 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -363,14 +363,59 @@
 	return size;
 }
 
+static int run_slot(struct active_request_slot *slot)
+{
+	int err = 0;
+	struct slot_results results;
+
+	slot->results = &results;
+	slot->curl_result = curl_easy_perform(slot->curl);
+	finish_active_slot(slot);
+
+	if (results.curl_result != CURLE_OK) {
+		err |= error("RPC failed; result=%d, HTTP code = %ld",
+			results.curl_result, results.http_code);
+	}
+
+	return err;
+}
+
+static int probe_rpc(struct rpc_state *rpc)
+{
+	struct active_request_slot *slot;
+	struct curl_slist *headers = NULL;
+	struct strbuf buf = STRBUF_INIT;
+	int err;
+
+	slot = get_active_slot();
+
+	headers = curl_slist_append(headers, rpc->hdr_content_type);
+	headers = curl_slist_append(headers, rpc->hdr_accept);
+
+	curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 0);
+	curl_easy_setopt(slot->curl, CURLOPT_POST, 1);
+	curl_easy_setopt(slot->curl, CURLOPT_URL, rpc->service_url);
+	curl_easy_setopt(slot->curl, CURLOPT_ENCODING, "");
+	curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDS, "0000");
+	curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDSIZE, 4);
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, headers);
+	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
+	curl_easy_setopt(slot->curl, CURLOPT_FILE, &buf);
+
+	err = run_slot(slot);
+
+	curl_slist_free_all(headers);
+	strbuf_release(&buf);
+	return err;
+}
+
 static int post_rpc(struct rpc_state *rpc)
 {
 	struct active_request_slot *slot;
-	struct slot_results results;
 	struct curl_slist *headers = NULL;
 	int use_gzip = rpc->gzip_request;
 	char *gzip_body = NULL;
-	int err = 0, large_request = 0;
+	int err, large_request = 0;
 
 	/* Try to load the entire request, if we can fit it into the
 	 * allocated buffer space we can use HTTP/1.0 and avoid the
@@ -393,8 +438,13 @@
 		rpc->len += n;
 	}
 
+	if (large_request) {
+		err = probe_rpc(rpc);
+		if (err)
+			return err;
+	}
+
 	slot = get_active_slot();
-	slot->results = &results;
 
 	curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 0);
 	curl_easy_setopt(slot->curl, CURLOPT_POST, 1);
@@ -408,7 +458,7 @@
 		/* The request body is large and the size cannot be predicted.
 		 * We must use chunked encoding to send it.
 		 */
-		headers = curl_slist_append(headers, "Expect: 100-continue");
+		headers = curl_slist_append(headers, "Expect:");
 		headers = curl_slist_append(headers, "Transfer-Encoding: chunked");
 		rpc->initial_buffer = 1;
 		curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, rpc_out);
@@ -482,13 +532,7 @@
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, rpc_in);
 	curl_easy_setopt(slot->curl, CURLOPT_FILE, rpc);
 
-	slot->curl_result = curl_easy_perform(slot->curl);
-	finish_active_slot(slot);
-
-	if (results.curl_result != CURLE_OK) {
-		err |= error("RPC failed; result=%d, HTTP code = %ld",
-			results.curl_result, results.http_code);
-	}
+	err = run_slot(slot);
 
 	curl_slist_free_all(headers);
 	free(gzip_body);