diff --git a/src/js/_enqueues/admin/site-icon.js b/src/js/_enqueues/admin/site-icon.js
index a658f16e0b61a..49c6504156b59 100644
--- a/src/js/_enqueues/admin/site-icon.js
+++ b/src/js/_enqueues/admin/site-icon.js
@@ -117,6 +117,11 @@
 			// Grab the selected attachment.
 			var attachment = frame.state().get( 'selection' ).first();
 
+			if ( 'image' !== attachment.attributes.type ) {
+				window.alert( wp.i18n.__( 'The uploaded file is not a valid image. Please select a valid file format.' ) );
+				return;
+			}
+
 			if (
 				attachment.attributes.height === $el.data( 'size' ) &&
 				$el.data( 'size' ) === attachment.attributes.width
diff --git a/src/js/_enqueues/wp/customize/controls.js b/src/js/_enqueues/wp/customize/controls.js
index 921983e6bf78d..f8ed7d6b666da 100644
--- a/src/js/_enqueues/wp/customize/controls.js
+++ b/src/js/_enqueues/wp/customize/controls.js
@@ -4571,6 +4571,11 @@
 		onSelect: function() {
 			var attachment = this.frame.state().get( 'selection' ).first().toJSON();
 
+			if ( 'image' !== attachment.type ) {
+				window.alert( wp.i18n.__( 'The uploaded file is not a valid image. Please select a valid file format.' ) );
+				return;
+			}
+
 			if ( this.params.width === attachment.width && this.params.height === attachment.height && ! this.params.flex_width && ! this.params.flex_height ) {
 				this.setImageFromAttachment( attachment );
 				this.frame.close();
@@ -4791,6 +4796,11 @@
 			var attachment = this.frame.state().get( 'selection' ).first().toJSON(),
 				controller = this;
 
+			if ( 'image' !== attachment.type ) {
+				window.alert( wp.i18n.__( 'The uploaded file is not a valid image. Please select a valid file format.' ) );
+				return;
+			}
+
 			if ( this.params.width === attachment.width && this.params.height === attachment.height && ! this.params.flex_width && ! this.params.flex_height ) {
 				wp.ajax.post( 'crop-image', {
 					nonce: attachment.nonces.edit,
@@ -5060,6 +5070,13 @@
 		 * switch to the cropper state.
 		 */
 		onSelect: function() {
+			var attachment = this.frame.state().get( 'selection' ).first().toJSON();
+
+			if ( 'image' !== attachment.type ) {
+				window.alert( wp.i18n.__( 'The uploaded file is not a valid image. Please select a valid file format.' ) );
+				return;
+			}
+
 			this.frame.setState('cropper');
 		},