diff --git a/src/observable/map/MappedMap.js b/src/observable/map/MappedMap.js
index 96cec32e..51a23d41 100644
--- a/src/observable/map/MappedMap.js
+++ b/src/observable/map/MappedMap.js
@@ -16,7 +16,7 @@ limitations under the License.
 
 import {BaseObservableMap} from "./BaseObservableMap.js";
 /*
-so a mapped value can emit updates on it's own with this._updater that is passed in the mapping function
+so a mapped value can emit updates on it's own with this._emitSpontaneousUpdate that is passed in the mapping function
 how should the mapped value be notified of an update though? and can it then decide to not propagate the update?
 */
 export class MappedMap extends BaseObservableMap {
@@ -25,14 +25,18 @@ export class MappedMap extends BaseObservableMap {
         this._source = source;
         this._mapper = mapper;
         this._mappedValues = new Map();
-        this._updater = (key, params) => {  // this should really be (value, params) but can't make that work for now
-            const value = this._mappedValues.get(key);
-            this.onUpdate(key, value, params);
-        };
+    }
+
+    _emitSpontaneousUpdate(key, params) {
+        const value = this._mappedValues.get(key);
+        if (value) {
+            this.emitUpdate(key, value, params);
+        }
     }
 
     onAdd(key, value) {
-        const mappedValue = this._mapper(value, this._updater);
+        const emitSpontaneousUpdate = this._emitSpontaneousUpdate.bind(this, key);
+        const mappedValue = this._mapper(value, emitSpontaneousUpdate);
         this._mappedValues.set(key, mappedValue);
         this.emitAdd(key, mappedValue);
     }
@@ -47,17 +51,16 @@ export class MappedMap extends BaseObservableMap {
     onUpdate(key, value, params) {
         const mappedValue = this._mappedValues.get(key);
         if (mappedValue !== undefined) {
-            const newParams = this._updater(value, params);
-            // if (newParams !== undefined) {
-                this.emitUpdate(key, mappedValue, newParams);
-            // }
+            // TODO: map params somehow if needed?
+            this.emitUpdate(key, mappedValue, params);
         }
     }
 
     onSubscribeFirst() {
         this._subscription = this._source.subscribe(this);
         for (let [key, value] of this._source) {
-            const mappedValue = this._mapper(value, this._updater);
+            const emitSpontaneousUpdate = this._emitSpontaneousUpdate.bind(this, key);
+            const mappedValue = this._mapper(value, emitSpontaneousUpdate);
             this._mappedValues.set(key, mappedValue);
         }
         super.onSubscribeFirst();