Index: src/wp-admin/js/customize-controls.js
===================================================================
--- src/wp-admin/js/customize-controls.js	(revision 36678)
+++ src/wp-admin/js/customize-controls.js	(working copy)
@@ -2331,6 +2331,13 @@
 				api.HeaderTool.UploadsList,
 				api.HeaderTool.DefaultsList
 			]);
+
+			// Fix ajax issue in customizer when previwing different theme which supports header image in customizer 
+			$.ajaxPrefilter(function( options, originalOptions, jqXHR ) {
+			  	if ( 'custom-header-crop' === originalOptions.data.action ){
+		  			options.data += '&wp_customize=on&theme=' + api.settings.theme.stylesheet;
+			  	}
+			});
 		},
 
 		/**