diff --git a/application/src/main/java/run/halo/app/content/HtmlThumbnailSrcsetInjector.java b/application/src/main/java/run/halo/app/content/HtmlThumbnailSrcsetInjector.java
index 55226e6af55..ccb03b81944 100644
--- a/application/src/main/java/run/halo/app/content/HtmlThumbnailSrcsetInjector.java
+++ b/application/src/main/java/run/halo/app/content/HtmlThumbnailSrcsetInjector.java
@@ -45,13 +45,17 @@ public static Mono<String> injectSrcset(String html,
     static String buildSizesAttr() {
         var sb = new StringBuilder();
         var delimiter = ", ";
-        for (ThumbnailSize size : ThumbnailSize.values()) {
-            sb.append("(max-width: ").append(size.getWidth()).append("px) ")
+        var sizes = ThumbnailSize.values();
+        for (int i = 0; i < sizes.length; i++) {
+            var size = sizes[i];
+            sb.append("(max-width: ").append(size.getWidth()).append("px)")
+                .append(" ")
                 .append(size.getWidth())
-                .append("px")
-                .append(delimiter);
+                .append("px");
+            if (i < sizes.length - 1) {
+                sb.append(delimiter);
+            }
         }
-        sb.deleteCharAt(sb.length() - delimiter.length());
         return sb.toString();
     }
 
diff --git a/application/src/test/java/run/halo/app/content/HtmlThumbnailSrcsetInjectorTest.java b/application/src/test/java/run/halo/app/content/HtmlThumbnailSrcsetInjectorTest.java
index 3c4dbeefd37..5976457863a 100644
--- a/application/src/test/java/run/halo/app/content/HtmlThumbnailSrcsetInjectorTest.java
+++ b/application/src/test/java/run/halo/app/content/HtmlThumbnailSrcsetInjectorTest.java
@@ -25,9 +25,11 @@ void injectSrcset() {
             """;
         var result = HtmlThumbnailSrcsetInjector.injectSrcset(html,
             src -> Mono.just(src + " 480w, " + src + " 800w")).block();
-        assertThat(result).isEqualTo("""
+        assertThat(result).isEqualToIgnoringWhitespace("""
             <div>
-              <img src="image1.jpg" alt="test" srcset="image1.jpg 480w, image1.jpg 800w">
+              <img src="image1.jpg" alt="test" srcset="image1.jpg 480w, image1.jpg 800w"\
+                sizes="(max-width: 400px) 400px, (max-width: 800px) 800px,\
+                 (max-width: 1200px) 1200px, (max-width: 1600px) 1600px">
               <img src="image2.jpg" srcset="image2-small.jpg 480w, image2-large.jpg 800w">
             </div>
             """);