diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 0b7608c..dbc2593 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1851,7 +1851,7 @@ function theme_dropbutton_wrapper($variables) {
 }
 
 /**
- * Prepares variables for an image.
+ * Prepares variables for image templates.
  *
  * Default template: image.html.twig.
  *
@@ -1884,6 +1884,9 @@ function template_preprocess_image(&$variables) {
       $attributes[$key] = $variables[$key];
     }
   }
+  // Remove 'image' from the class array. This is added through
+  // template_preprocess() but we do not need it.
+  $attributes['class'] = array_diff($attributes['class'], array('image'));
 
   $variables['attributes'] = new Attribute($attributes);
 }
diff --git a/core/modules/image/lib/Drupal/image/Tests/ImageDimensionsTest.php b/core/modules/image/lib/Drupal/image/Tests/ImageDimensionsTest.php
index e7552d2..b4be34b 100644
--- a/core/modules/image/lib/Drupal/image/Tests/ImageDimensionsTest.php
+++ b/core/modules/image/lib/Drupal/image/Tests/ImageDimensionsTest.php
@@ -70,7 +70,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" width="120" height="60" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" width="120" height="60" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -91,7 +91,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" width="60" height="120" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" width="60" height="120" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -113,7 +113,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" width="45" height="90" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" width="45" height="90" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -135,7 +135,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" width="45" height="90" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" width="45" height="90" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -153,7 +153,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" width="45" height="90" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" width="45" height="90" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -174,7 +174,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -194,7 +194,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" width="30" height="30" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" width="30" height="30" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -215,7 +215,7 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" alt=""/>');
     $this->assertFalse(file_exists($generated_uri), 'Generated file does not exist.');
     $this->drupalGet($url);
     $this->assertResponse(200, 'Image was generated at the URL.');
@@ -233,6 +233,6 @@ function testImageDimensions() {
 
     image_effect_save($style, $effect);
     $img_tag = theme_image_style($variables);
-    $this->assertEqual($img_tag, '<img class="image-style-test" src="' . $url . '" alt="" />');
+    $this->assertEqual(trim($img_tag), '<img class="image-style-test" src="' . $url . '" alt=""/>');
   }
 }
diff --git a/core/modules/system/templates/image.html.twig b/core/modules/system/templates/image.html.twig
index d3234da..0263101 100644
--- a/core/modules/system/templates/image.html.twig
+++ b/core/modules/system/templates/image.html.twig
@@ -1,10 +1,10 @@
 {#
 /**
  * @file
- * Default theme implementation an image.
+ * Default theme implementation of an image.
  *
  * Available variables:
- *   - attributes: Associative array of attributes to be placed in the img tag.
+ *   - attributes: An array of HTML attributes for the img tag.
  *
  * @see template_preprocess()
  * @see template_preprcoess_image()
@@ -12,4 +12,4 @@
  * @ingroup themable
  */
 #}
-<img {{ attributes }}/>
+<img{{ attributes }}/>