diff --git a/apps/tests/xml-declaration/xml-declaration-tests.ts b/apps/tests/xml-declaration/xml-declaration-tests.ts
index a932e97b5..54385ba32 100644
--- a/apps/tests/xml-declaration/xml-declaration-tests.ts
+++ b/apps/tests/xml-declaration/xml-declaration-tests.ts
@@ -152,6 +152,17 @@ export function test_parse_ShouldParsePlatformSpecificComponents() {
     }
 };
 
+export function test_parse_ThrowErrorWhenNestingPlatforms() {
+    var e: Error;
+    try {
+        builder.parse("<Page><ios><TextField /><android><Label /></android></ios></Page>");
+    } catch (ex) {
+        e = ex;
+    }
+    
+    TKUnit.assert(e, "Expected result: Error; Actual result: " + e);
+};
+
 export function test_parse_ShouldParseBindings() {
     var p = <page.Page>builder.parse("<Page><Switch checked='{{ myProp }}' /></Page>");
     p.bindingContext = { myProp: true };
diff --git a/ui/builder/builder.ts b/ui/builder/builder.ts
index 76c1887a3..c0de226fd 100644
--- a/ui/builder/builder.ts
+++ b/ui/builder/builder.ts
@@ -49,15 +49,16 @@ function parseInternal(value: string, exports: any): componentBuilder.ComponentM
 
         if (args.eventType === xml.ParserEventType.StartElement) {
             if (isPlatform(args.elementName)) {
+
+                if (currentPlatformContext) {
+                    throw new Error("Already in '" + currentPlatformContext + "' platform context and cannot switch to '" + args.elementName + "' platform! Platform tags cannot be nested.");
+                }
+
                 currentPlatformContext = args.elementName;
                 return;
             }
         }
 
-        if (currentPlatformContext && !isCurentPlatform(currentPlatformContext)) {
-            return;
-        }
-
         if (args.eventType === xml.ParserEventType.EndElement) {
             if (isPlatform(args.elementName)) {
                 currentPlatformContext = undefined;
@@ -65,6 +66,10 @@ function parseInternal(value: string, exports: any): componentBuilder.ComponentM
             }
         }
 
+        if (currentPlatformContext && !isCurentPlatform(currentPlatformContext)) {
+            return;
+        }
+
         if (templateBuilder) {
             if (args.eventType === xml.ParserEventType.StartElement) {
                 templateBuilder.addStartElement(args.prefix, args.namespace, args.elementName, args.attributes);