diff --git a/modules/core/difference.js b/modules/core/difference.js
index 726060aa4..425540226 100644
--- a/modules/core/difference.js
+++ b/modules/core/difference.js
@@ -73,14 +73,30 @@ export function coreDifference(base, head) {
     _diff.didChange = _didChange;
 
 
-    _diff.extantIDs = function extantIDs() {
-        var result = [];
+    // pass true to include affected relation members
+    _diff.extantIDs = function extantIDs(includeRelMembers) {
+        var result = new Set();
         Object.keys(_changes).forEach(function(id) {
             if (_changes[id].head) {
-                result.push(id);
+                result.add(id);
+            }
+
+            var h = _changes[id].head;
+            var b = _changes[id].base;
+            var entity = h || b;
+
+            if (includeRelMembers && entity.type === 'relation') {
+                var mh = h ? h.members.map(function(m) { return m.id; }) : [];
+                var mb = b ? b.members.map(function(m) { return m.id; }) : [];
+                utilArrayUnion(mh, mb).forEach(function(memberID) {
+                    if (head.hasEntity(memberID)) {
+                        result.add(memberID);
+                    }
+                });
             }
         });
-        return result;
+
+        return Array.from(result);
     };
 
 
diff --git a/modules/core/validator.js b/modules/core/validator.js
index e85240e3d..73dbe93b5 100644
--- a/modules/core/validator.js
+++ b/modules/core/validator.js
@@ -292,8 +292,12 @@ export function coreValidator(context) {
 
             if (entity.type === 'node') {   // include parent ways
                 graph.parentWays(entity).forEach(function(parentWay) {
-                    checkParentRels.push(parentWay);
                     acc.add(parentWay.id);
+                    checkParentRels.push(parentWay);
+                });
+            } else if (entity.type === 'relation') {   // include members
+                entity.members.forEach(function(member) {
+                    acc.add(member.id);
                 });
             }
 
@@ -356,8 +360,8 @@ export function coreValidator(context) {
             }
         }
 
-        var entityIDs = difference.extantIDs();  // created and modified
-        difference.deleted().forEach(uncacheEntityID);   // deleted
+        var entityIDs = difference.extantIDs(true);   // created/modified (true = w/relation members)
+        difference.deleted().forEach(uncacheEntityID);  // deleted
 
         validator.validateEntities(entityIDs);   // dispatches 'validated'
     };
diff --git a/test/spec/core/difference.js b/test/spec/core/difference.js
index 45ae6e04c..a5062e745 100644
--- a/test/spec/core/difference.js
+++ b/test/spec/core/difference.js
@@ -118,6 +118,36 @@ describe('iD.coreDifference', function () {
             var diff = iD.coreDifference(base, head);
             expect(diff.extantIDs()).to.eql([]);
         });
+
+        it('omits the ids of members of modified relations by default', function () {
+            var w1 = iD.osmWay({id: 'w1'});
+            var w2 = iD.osmWay({id: 'w2'});
+            var r1 = iD.osmRelation({
+                id: 'r',
+                tags: { type: 'multipolygon' },
+                members: [{role: 'outer', id: 'w1', type: 'way'}, {role: '', id: 'w2', type: 'way'}]
+            });
+            var r2 = r1.update({ tags: { type: 'multipolygon', landuse: 'residential' }});
+            var base = iD.coreGraph([r1, w1, w2]);
+            var head = base.replace(r2);
+            var diff = iD.coreDifference(base, head);
+            expect(diff.extantIDs()).to.eql(['r']);
+        });
+
+        it('includes the ids of members of modified relations with option', function () {
+            var w1 = iD.osmWay({id: 'w1'});
+            var w2 = iD.osmWay({id: 'w2'});
+            var r1 = iD.osmRelation({
+                id: 'r',
+                tags: { type: 'multipolygon' },
+                members: [{role: 'outer', id: 'w1', type: 'way'}, {role: '', id: 'w2', type: 'way'}]
+            });
+            var r2 = r1.update({ tags: { type: 'multipolygon', landuse: 'residential' }});
+            var base = iD.coreGraph([r1, w1, w2]);
+            var head = base.replace(r2);
+            var diff = iD.coreDifference(base, head);
+            expect(diff.extantIDs(true)).to.eql(['r', 'w1', 'w2']);
+        });
     });
 
     describe('#created', function () {