diff --git a/js/id/core/entity.js b/js/id/core/entity.js
index 8ea60bb31..b0ed5b0f0 100644
--- a/js/id/core/entity.js
+++ b/js/id/core/entity.js
@@ -73,7 +73,7 @@ iD.Entity.prototype = {
             var t1 = merged[k],
                 t2 = tags[k];
             if (t1 && t1 !== t2) {
-                merged[k] = t1 + ';' + t2;
+                merged[k] = _.union(t1.split(/;\s*/), t2.split(/;\s*/)).join(';');
             } else {
                 merged[k] = t2;
             }
diff --git a/test/spec/core/entity.js b/test/spec/core/entity.js
index 51a89dee4..2cc3cce05 100644
--- a/test/spec/core/entity.js
+++ b/test/spec/core/entity.js
@@ -88,6 +88,22 @@ describe('iD.Entity', function () {
                 b = a.mergeTags({a: 'b'});
             expect(b.tags).to.eql({a: 'a;b'});
         });
+
+        it("combines combined tags", function () {
+            var a = iD.Entity({tags: {a: 'a;b'}}),
+                b = iD.Entity({tags: {a: 'b'}});
+
+            expect(a.mergeTags(b.tags).tags).to.eql({a: 'a;b'});
+            expect(b.mergeTags(a.tags).tags).to.eql({a: 'b;a'});
+        });
+
+        it("combines combined tags with whitespace", function () {
+            var a = iD.Entity({tags: {a: 'a; b'}}),
+                b = iD.Entity({tags: {a: 'b'}});
+
+            expect(a.mergeTags(b.tags).tags).to.eql({a: 'a;b'});
+            expect(b.mergeTags(a.tags).tags).to.eql({a: 'b;a'});
+        });
     });
 
     describe("#osmId", function () {