diff --git a/prog/weaver/http.go b/prog/weaver/http.go
index a0cca5c88d..c02b2bdb6d 100644
--- a/prog/weaver/http.go
+++ b/prog/weaver/http.go
@@ -246,7 +246,13 @@ func HandleHTTP(muxRouter *mux.Router, version string, router *weave.NetworkRout
 
 	muxRouter.Methods("GET").Path("/report").Queries("format", "{format}").HandlerFunc(
 		func(w http.ResponseWriter, r *http.Request) {
-			formatTemplate, err := template.New("format").Parse(mux.Vars(r)["format"])
+			funcs := template.FuncMap{
+				"json": func(v interface{}) string {
+					a, _ := json.Marshal(v)
+					return string(a)
+				},
+			}
+			formatTemplate, err := template.New("format").Funcs(funcs).Parse(mux.Vars(r)["format"])
 			if err != nil {
 				http.Error(w, err.Error(), http.StatusBadRequest)
 				return
diff --git a/site/troubleshooting.md b/site/troubleshooting.md
index 22b81758e0..30d5919eaf 100644
--- a/site/troubleshooting.md
+++ b/site/troubleshooting.md
@@ -232,6 +232,12 @@ inspect`:
     $ weave report -f {% raw %}'{{.DNS.Domain}}'{% endraw %}
     weave.local.
 
+Weave adds a template function, `json`, which can be applied to get
+results in JSON format.
+
+    $ weave report -f {% raw %}'{{json .DNS}}'{% endraw %}
+    {% raw %}{"Domain":"weave.local.","Upstream":["8.8.8.8","8.8.4.4"],"Address":"172.17.0.1:53","TTL":1,"Entries":null}{% endraw %}
+
 ### <a name="list-attached-containers"></a>List attached containers
 
     weave ps