diff --git a/src/MappedCollection.coffee b/src/MappedCollection.coffee
index 1abb9f0ac..c2ebb61e2 100644
--- a/src/MappedCollection.coffee
+++ b/src/MappedCollection.coffee
@@ -176,6 +176,8 @@ class $MappedCollection
 
       rule.value = def.value
 
+      rule.private = !!def.private
+
       @_rules[name] = rule
       @_hooks[name] =
         enter: []
diff --git a/src/main.coffee b/src/main.coffee
index c7c2c5399..611757e31 100644
--- a/src/main.coffee
+++ b/src/main.coffee
@@ -55,7 +55,12 @@ $handleJsonRpcCall = (api, session, encodedRequest) ->
     )
 
   # Checks it is a compliant JSON-RPC 2.0 request.
-  if not request.method or not request.params or request.id is undefined or request.jsonrpc isnt '2.0'
+  if (
+    not request.method? or
+    not request.params? or
+    not request.id? or
+    request.jsonrpc isnt '2.0'
+  )
     return formatError $API.err.INVALID_REQUEST
 
   # Executes the requested method on the API.
diff --git a/src/spec.coffee b/src/spec.coffee
index 9f5dbe562..9bdceb1fe 100644
--- a/src/spec.coffee
+++ b/src/spec.coffee
@@ -61,8 +61,8 @@ module.exports = (refsToUUIDs) ->
           $CPUs: @dynamic 0,
             host:
               # No `update`: `exit` then `enter` will be called instead.
-              enter: (host) -> @field += parseInt(host.CPUs["cpu_count"])
-              exit:  (host) -> @field -= parseInt(host.CPUs["cpu_count"])
+              enter: (host) -> @field += +host.CPUs["cpu_count"]
+              exit:  (host) -> @field -= +host.CPUs["cpu_count"]
 
           $running_VMs: @dynamic [],
             VM:
@@ -370,7 +370,7 @@ module.exports = (refsToUUIDs) ->
                 {power_state: state} = @value
                 return unless state in ['Paused', 'Running']
 
-                @field.number = metrics.VCPUs_number
+                @field.number = +metrics.VCPUs_number
             }
           }
 
@@ -543,5 +543,6 @@ module.exports = (refsToUUIDs) ->
 
         test: test
 
-        value: -> @generator
         private: true
+
+        value: -> @generator