diff --git a/includes/class-woocommerce.php b/includes/class-woocommerce.php
index a07a42210ad..f4a3bcb5c45 100644
--- a/includes/class-woocommerce.php
+++ b/includes/class-woocommerce.php
@@ -539,11 +539,13 @@ final class WooCommerce {
 	 * @since 2.3
 	 */
 	public function add_image_sizes() {
-		$thumbnail = wc_get_image_size( 'thumbnail' );
-		$single    = wc_get_image_size( 'single' );
+		$thumbnail         = wc_get_image_size( 'thumbnail' );
+		$single            = wc_get_image_size( 'single' );
+		$gallery_thumbnail = wc_get_image_size( 'gallery_thumbnail' );
 
 		add_image_size( 'woocommerce_thumbnail', $thumbnail['width'], $thumbnail['height'], $thumbnail['crop'] );
 		add_image_size( 'woocommerce_single', $single['width'], $single['height'], $single['crop'] );
+		add_image_size( 'woocommerce_gallery_thumbnail', $gallery_thumbnail['width'], $gallery_thumbnail['height'], $gallery_thumbnail['crop'] );
 
 		// 2x thumbnail size for retina, and when showing less columns.
 		add_image_size( 'woocommerce_thumbnail_2x', $thumbnail['width'] * 2, '' !== $thumbnail['height'] ? $thumbnail['height'] * 2 : '', $thumbnail['crop'] );
diff --git a/includes/customizer/class-wc-shop-customizer.php b/includes/customizer/class-wc-shop-customizer.php
index 6631483934e..31c5351ced2 100644
--- a/includes/customizer/class-wc-shop-customizer.php
+++ b/includes/customizer/class-wc-shop-customizer.php
@@ -156,7 +156,7 @@ class WC_Shop_Customizer {
 					setting.bind( function( value ) {
 						var min = parseInt( '<?php echo esc_js( $min_rows ); ?>', 10 );
 						var max = parseInt( '<?php echo esc_js( $max_rows ); ?>', 10 );
-						
+
 						value = parseInt( value, 10 );
 
 						if ( max && value > max ) {
@@ -496,7 +496,7 @@ class WC_Shop_Customizer {
 				'woocommerce_thumbnail_image_width',
 				array(
 					'label'       => __( 'Thumbnail width', 'woocommerce' ),
-					'description' => __( 'Image size used for products in the catalog and product gallery thumbnails.', 'woocommerce' ),
+					'description' => __( 'Image size used for products in the catalog.', 'woocommerce' ),
 					'section'     => 'woocommerce_product_images',
 					'settings'    => 'woocommerce_thumbnail_image_width',
 					'type'        => 'number',
diff --git a/includes/wc-core-functions.php b/includes/wc-core-functions.php
index 32e377518af..d118cdec82d 100644
--- a/includes/wc-core-functions.php
+++ b/includes/wc-core-functions.php
@@ -722,6 +722,13 @@ function wc_get_image_size( $image_size ) {
 		'crop'   => 1,
 	);
 
+	// Size mapping.
+	if ( in_array( $image_size, array( 'shop_single', 'woocommerce_single' ), true ) ) {
+		$image_size = 'single';
+	} elseif ( in_array( $image_size, array( 'shop_thumbnail', 'shop_catalog', 'woocommerce_thumbnail' ), true ) ) {
+		$image_size = 'thumbnail';
+	}
+
 	if ( is_array( $image_size ) ) {
 		$size       = array(
 			'width'  => isset( $image_size[0] ) ? absint( $image_size[0] ) : 600,
@@ -729,12 +736,18 @@ function wc_get_image_size( $image_size ) {
 			'crop'   => isset( $image_size[2] ) ? absint( $image_size[2] ) : 1,
 		);
 		$image_size = $size['width'] . '_' . $size['height'];
-	} elseif ( in_array( $image_size, array( 'single', 'shop_single', 'woocommerce_single' ), true ) ) {
+
+	} elseif ( 'single' === $image_size ) {
 		$size['width']  = absint( wc_get_theme_support( 'single_image_width', get_option( 'woocommerce_single_image_width', 600 ) ) );
 		$size['height'] = '';
 		$size['crop']   = 0;
-		$image_size     = 'single';
-	} elseif ( in_array( $image_size, array( 'thumbnail', 'shop_thumbnail', 'shop_catalog', 'woocommerce_thumbnail' ), true ) ) {
+
+	} elseif ( 'gallery_thumbnail' === $image_size ) {
+		$size['width']  = absint( wc_get_theme_support( 'gallery_thumbnail_image_width', 100 ) );
+		$size['height'] = $size['width'];
+		$size['crop']   = 1;
+
+	} elseif ( 'thumbnail' === $image_size ) {
 		$size['width'] = absint( wc_get_theme_support( 'thumbnail_image_width', get_option( 'woocommerce_thumbnail_image_width', 300 ) ) );
 		$cropping      = get_option( 'woocommerce_thumbnail_cropping', '1:1' );
 
@@ -753,7 +766,6 @@ function wc_get_image_size( $image_size ) {
 			$size['height'] = round( ( $size['width'] / $width ) * $height );
 			$size['crop']   = 1;
 		}
-		$image_size = 'thumbnail';
 	}
 
 	return apply_filters( 'woocommerce_get_image_size_' . $image_size, $size );