diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 40c90bc25e3c..ccecb2132643 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -2553,7 +2553,7 @@ object Parsers {
      */
     def newExpr(): Tree =
       val start = in.skipToken()
-      def reposition(t: Tree) = t.withSpan(Span(start, in.lastOffset))
+      def reposition(t: Tree) = t.withSpan(Span(start, in.lastCharOffset))
       possibleTemplateStart()
       val parents =
         if in.isNestedStart then Nil
diff --git a/tests/neg/i18265.check b/tests/neg/i18265.check
new file mode 100644
index 000000000000..8f9df80f77dc
--- /dev/null
+++ b/tests/neg/i18265.check
@@ -0,0 +1,6 @@
+-- [E019] Syntax Error: tests/neg/i18265.scala:5:13 ----------------------------
+5 |    def twice
+  |             ^
+  |             Missing return type
+  |
+  | longer explanation available when compiling with `-explain`
\ No newline at end of file
diff --git a/tests/neg/i18265.scala b/tests/neg/i18265.scala
new file mode 100644
index 000000000000..e937a5203ecb
--- /dev/null
+++ b/tests/neg/i18265.scala
@@ -0,0 +1,5 @@
+trait Foo
+
+val foo = new Foo:
+  extension (s: String)
+    def twice
\ No newline at end of file