diff --git a/lib/rufo/erb_formatter.rb b/lib/rufo/erb_formatter.rb
index 2509c619..fb9d9d53 100644
--- a/lib/rufo/erb_formatter.rb
+++ b/lib/rufo/erb_formatter.rb
@@ -90,7 +90,7 @@ def process_erb
   end
 
   def process_code(code_str)
-    sexps = Ripper.sexp(code_str)
+    sexps = Ripper.sexp(code_str) || Rufo::Parser.sexp_unparsable_code(code_str)
     if sexps.nil?
       prefix, suffix = determine_code_wrappers(code_str)
     end
@@ -157,6 +157,7 @@ def determine_code_wrappers(code_str)
     return "begin\n", "\nend" if Ripper.sexp("begin\n#{code_str}\nend")
     return "if a\n", "\nend" if Ripper.sexp("if a\n#{code_str}\nend")
     return "case a\n", "\nend" if Ripper.sexp("case a\n#{code_str}\nend")
+    return nil, "\nwhen nil\nend" if Ripper.sexp("#{code_str}\nwhen nil\nend")
     raise_syntax_error!(code_str)
   end
 
diff --git a/spec/lib/rufo/erb_formatter_spec.rb b/spec/lib/rufo/erb_formatter_spec.rb
index f00ed0ba..c7fbfa21 100644
--- a/spec/lib/rufo/erb_formatter_spec.rb
+++ b/spec/lib/rufo/erb_formatter_spec.rb
@@ -90,6 +90,16 @@
       expect(result).to eql("<%= yield %>")
     end
 
+    it "formats standalone 'yield' with arguments" do
+      result = subject.format("<%=yield x,y%>")
+      expect(result).to eql("<%= yield x, y %>")
+    end
+
+    it "formats standalone 'yield' with arguments and parens" do
+      result = subject.format("<%=yield(x,y)%>")
+      expect(result).to eql("<%= yield(x, y) %>")
+    end
+
     it "handles native erb comments" do
       result = subject.format("<%# locals: (item:, variant:) %>")
       expect(result).to eql("<%# locals: (item:, variant:) %>")
@@ -119,5 +129,20 @@
       result = subject.format("<% - x * y %>")
       expect(result).to eql("<% -x * y %>")
     end
+
+    it "handles case/when expression" do
+      result = subject.format(<<~ERB)
+        <% case a+b %>
+        <% when c %>
+        <%= d+e %>
+        <% end %>
+      ERB
+      expect(result).to eql(<<~ERB)
+                          <% case a + b %>
+                          <% when c %>
+                          <%= d + e %>
+                          <% end %>
+                        ERB
+    end
   end
 end