diff --git a/src/plugins/clangformat/clangformatbaseindenter.cpp b/src/plugins/clangformat/clangformatbaseindenter.cpp
index e210263770f..fa95514ca32 100644
--- a/src/plugins/clangformat/clangformatbaseindenter.cpp
+++ b/src/plugins/clangformat/clangformatbaseindenter.cpp
@@ -300,8 +300,8 @@ int forceIndentWithExtraText(QByteArray &buffer,
         if (block.previous().isValid()) {
             const int prevEndOffset = Utils::Text::utf8NthLineOffset(block.document(), buffer,
                     block.blockNumber()) + block.previous().text().length();
-            buffer.insert(prevEndOffset, "//");
-            extraLength += 2;
+            buffer.insert(prevEndOffset, " //");
+            extraLength += 3;
         }
     }
     buffer.insert(utf8Offset + extraLength, dummyText);
diff --git a/tests/unit/unittest/clangformat-test.cpp b/tests/unit/unittest/clangformat-test.cpp
index b6312866927..9aec542edfd 100644
--- a/tests/unit/unittest/clangformat-test.cpp
+++ b/tests/unit/unittest/clangformat-test.cpp
@@ -957,7 +957,7 @@ TEST_F(ClangFormat, ChainedMemberFunctionCalls)
                                              "    .func();"));
 }
 
-TEST_F(ClangFormat, DISABLED_CommentBlock)
+TEST_F(ClangFormat, CommentBlock)
 {
     insertLines({"/****************************************************************************",
                  "**",