diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
index d11e17e2c9..a0e1fc24f4 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
@@ -702,7 +702,9 @@ class Router(formatOps: FormatOps) {
             case Newlines.unfold =>
               val rightParent = rightOwner.parent.get
               val slbEnd =
-                if (defn) beforeDefRhs.fold(getLastToken(rightParent))(_.left)
+                if (defn)
+                  beforeDefRhs
+                    .fold(getLastToken(rightParent))(prevNonComment(_).left)
                 else getLastToken(getLastCall(rightParent))
               val multipleArgs = isSeqMulti(getArgs(next(ft).meta.leftOwner))
               val nft = tokens.tokenAfter(close)
diff --git a/scalafmt-tests/src/test/resources/scala3/OptionalBraces.stat b/scalafmt-tests/src/test/resources/scala3/OptionalBraces.stat
index be4f7b1c02..ec30509547 100644
--- a/scalafmt-tests/src/test/resources/scala3/OptionalBraces.stat
+++ b/scalafmt-tests/src/test/resources/scala3/OptionalBraces.stat
@@ -4590,3 +4590,15 @@ object Test:
      catch
         case _: RuntimeException => 2
         case _: Exception        => 3
+<<< #3497
+newlines.beforeOpenParenDefnSite = null
+===
+extension (s: String)
+  /** ... */
+  def foo(): Unit = ???
+  def bar(): Unit = ???
+>>>
+extension (s: String)
+   /** ... */
+   def foo(): Unit = ???
+   def bar(): Unit = ???
diff --git a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_fold.stat b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_fold.stat
index 36bb28b3d5..863f5d0685 100644
--- a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_fold.stat
+++ b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_fold.stat
@@ -4397,3 +4397,15 @@ object Test:
      catch
         case _: RuntimeException => 2
         case _: Exception        => 3
+<<< #3497
+newlines.beforeOpenParenDefnSite = fold
+===
+extension (s: String)
+  /** ... */
+  def foo(): Unit = ???
+  def bar(): Unit = ???
+>>>
+extension(s: String)
+   /** ... */
+   def foo(): Unit = ???
+   def bar(): Unit = ???
diff --git a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat
index 983f236de5..2bce0fccaa 100644
--- a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat
+++ b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat
@@ -4631,3 +4631,15 @@ object Test:
      catch
         case _: RuntimeException => 2
         case _: Exception        => 3
+<<< #3497
+newlines.beforeOpenParenDefnSite = keep
+===
+extension (s: String)
+  /** ... */
+  def foo(): Unit = ???
+  def bar(): Unit = ???
+>>>
+extension(s: String)
+   /** ... */
+   def foo(): Unit = ???
+   def bar(): Unit = ???
diff --git a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_unfold.stat b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_unfold.stat
index e9b6a345e2..26d2bccbe3 100644
--- a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_unfold.stat
+++ b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_unfold.stat
@@ -4733,3 +4733,15 @@ object Test:
           2
         case _: Exception =>
           3
+<<< #3497
+newlines.beforeOpenParenDefnSite = unfold
+===
+extension (s: String)
+  /** ... */
+  def foo(): Unit = ???
+  def bar(): Unit = ???
+>>>
+extension(s: String)
+   /** ... */
+   def foo(): Unit = ???
+   def bar(): Unit = ???