diff --git a/lib/ruby_lsp/requests/on_type_formatting.rb b/lib/ruby_lsp/requests/on_type_formatting.rb
index 1c6f876fb..cfe0c1f3b 100644
--- a/lib/ruby_lsp/requests/on_type_formatting.rb
+++ b/lib/ruby_lsp/requests/on_type_formatting.rb
@@ -63,7 +63,7 @@ def perform
           if (comment_match = @previous_line.match(/^#(\s*)/))
             handle_comment_line(T.must(comment_match[1]))
           elsif @document.syntax_error?
-            match = /(?<=<<(-|~))(?<quote>['"`]?)(?<delimiter>\w+)\k<quote>/.match(@previous_line)
+            match = /(<<((-|~)?))(?<quote>['"`]?)(?<delimiter>\w+)\k<quote>/.match(@previous_line)
             heredoc_delimiter = match && match.named_captures["delimiter"]
 
             if heredoc_delimiter
diff --git a/test/requests/on_type_formatting_test.rb b/test/requests/on_type_formatting_test.rb
index a6e4088b2..b808225eb 100644
--- a/test/requests/on_type_formatting_test.rb
+++ b/test/requests/on_type_formatting_test.rb
@@ -570,6 +570,76 @@ def test_adding_heredoc_delimiter
     assert_equal(expected_edits.to_json, T.must(edits).to_json)
   end
 
+  def test_plain_heredoc_completion
+    document = RubyLsp::RubyDocument.new(source: +"", version: 1, uri: URI("file:///fake.rb"))
+
+    document.push_edits(
+      [{
+        range: { start: { line: 0, character: 0 }, end: { line: 0, character: 0 } },
+        text: "str = <<STR",
+      }],
+      version: 2,
+    )
+    document.parse!
+
+    edits = RubyLsp::Requests::OnTypeFormatting.new(
+      document,
+      { line: 1, character: 2 },
+      "\n",
+      "Visual Studio Code",
+    ).perform
+    expected_edits = [
+      {
+        range: { start: { line: 1, character: 2 }, end: { line: 1, character: 2 } },
+        newText: "\n",
+      },
+      {
+        range: { start: { line: 1, character: 2 }, end: { line: 1, character: 2 } },
+        newText: "STR",
+      },
+      {
+        range: { start: { line: 1, character: 2 }, end: { line: 1, character: 2 } },
+        newText: "$0",
+      },
+    ]
+    assert_equal(expected_edits.to_json, T.must(edits).to_json)
+  end
+
+  def test_quoted_heredoc_completion
+    document = RubyLsp::RubyDocument.new(source: +"", version: 1, uri: URI("file:///fake.rb"))
+
+    document.push_edits(
+      [{
+        range: { start: { line: 0, character: 0 }, end: { line: 0, character: 0 } },
+        text: "str = <<-'STR'",
+      }],
+      version: 2,
+    )
+    document.parse!
+
+    edits = RubyLsp::Requests::OnTypeFormatting.new(
+      document,
+      { line: 1, character: 2 },
+      "\n",
+      "Visual Studio Code",
+    ).perform
+    expected_edits = [
+      {
+        range: { start: { line: 1, character: 2 }, end: { line: 1, character: 2 } },
+        newText: "\n",
+      },
+      {
+        range: { start: { line: 1, character: 2 }, end: { line: 1, character: 2 } },
+        newText: "STR",
+      },
+      {
+        range: { start: { line: 1, character: 2 }, end: { line: 1, character: 2 } },
+        newText: "$0",
+      },
+    ]
+    assert_equal(expected_edits.to_json, T.must(edits).to_json)
+  end
+
   def test_completing_end_token_inside_parameters
     document = RubyLsp::RubyDocument.new(source: +"foo(proc do\n)", version: 1, uri: URI("file:///fake.rb"))