diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -310,6 +310,8 @@
           for (; J != AnnotatedLines.begin(); --J)
             if ((*J)->Level < TheLine->Level)
               break;
+          if ((*J)->Level == TheLine->Level)
+            return false;
 
           // Check if the found line starts a record.
           const FormatToken *LastNonComment = (*J)->Last;
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -12639,6 +12639,13 @@
                "};",
                MergeInlineOnly);
   verifyFormat("int f() {}", MergeInlineOnly);
+  // https://llvm.org/PR54147
+  verifyFormat("auto lambda = []() {\n"
+               "  // comment\n"
+               "  f();\n"
+               "  g();\n"
+               "};",
+               MergeInlineOnly);
 
   // Also verify behavior when BraceWrapping.AfterFunction = true
   MergeInlineOnly.BreakBeforeBraces = FormatStyle::BS_Custom;