diff --git a/packages/ext-gen/appMigrate.js b/packages/ext-gen/appMigrate.js
index 942faed..23970a0 100644
--- a/packages/ext-gen/appMigrate.js
+++ b/packages/ext-gen/appMigrate.js
@@ -22,6 +22,10 @@ var gitIgnore = '.gitIgnore';
 var gitIgnoreAppend = '/generatedFiles ' + os.EOL + '/cordova ' + os.EOL + '/node_modules' + os.EOL;
 var gitIgnoreData = '/build ' + os.EOL + gitIgnoreAppend;
 var extFrameworkPath = 'node_modules/@sencha/ext';
+var themes = ['theme-base', 'theme-ios', 'theme-material',
+	'theme-aria', 'theme-neutral', 'theme-classic', 'theme-gray',
+	'theme-crisp', 'theme-crisp-touch', 'theme-neptune', 'theme-neptune-touch',
+	'theme-triton', 'theme-graphite'];
 var classic = false;
 var modern = false;
 var universal = false;
@@ -340,10 +344,6 @@ function removeDebugJsPath(jsonLocation) {
 
 function handleWorkspaceJsonmigrate() {
 	var workspaceJsonObject = getJson(workspaceJson),
-		themes = ['theme-base', 'theme-ios', 'theme-material',
-			'theme-aria', 'theme-neutral', 'theme-classic', 'theme-gray',
-			'theme-crisp', 'theme-crisp-touch', 'theme-neptune', 'theme-neptune-touch',
-			'theme-triton', 'theme-graphite'],
 		packageNames = ['treegrid', 'calendar', 'charts', 'froala-editor', 'amf', 'd3',
 			'exporter', 'pivot', 'pivot-d3', 'pivot-locale', 'ux', 'font-ios'],
 		basePath = '$\u007Bworkspace.dir}/node_modules/@sencha/ext-',
@@ -513,11 +513,11 @@ function buildToolKitAndThemeDetails() {
 	if (appJsonObject.hasOwnProperty('toolkit')) {
 		if (appJsonObject.toolkit == classicProfile) {
 			classic = true;
-			classicTheme = appJsonObject.theme;
+			classicTheme = appJsonObject.theme = verifyAndUpdateTheme(appJsonObject.theme);
 		}
 		else {
 			modern = true;
-			modernTheme = appJsonObject.theme;
+			modernTheme = appJsonObject.theme = verifyAndUpdateTheme(appJsonObject.theme);
 		}
 	}
 	else {
@@ -532,12 +532,32 @@ function buildToolKitAndThemeDetails() {
 		for (profile in appJsonObject.builds) {
 			if (profile === classicProfile) {
 				classic = true;
-				classicTheme = appJsonObject.builds[profile].theme;
+				classicTheme = appJsonObject.builds[profile].theme = verifyAndUpdateTheme(appJsonObject.builds[profile].theme);
 			}
 			if (profile == modernProfile) {
 				modern = true;
-				modernTheme = appJsonObject.builds[profile].theme;
+				modernTheme = appJsonObject.builds[profile].theme = verifyAndUpdateTheme(appJsonObject.builds[profile].theme);
 			}
 		}
 	}
 }
+
+function verifyAndUpdateTheme(appTheme) {
+	var themeStr = appTheme.replace(/[^a-z-]/g, ''),
+		       matchedTheme;
+
+	// once special chars are removed check if it is one of the existing themes 
+	if (themes.indexOf(themeStr) >= 0) {
+		return themeStr;
+	}
+	
+	// if doesn't exists return the appropriate theme from built-in theme list
+	for (var i = 0; i < themes.length; i++) {
+		if (themeStr.includes(themes[i])) {
+			matchedTheme = themes[i];
+			break;
+		}
+	}
+	return matchedTheme ? matchedTheme : appTheme;
+}
+