diff --git a/lib/steep/services/completion_provider.rb b/lib/steep/services/completion_provider.rb
index 7a9b542cd..12bd57127 100644
--- a/lib/steep/services/completion_provider.rb
+++ b/lib/steep/services/completion_provider.rb
@@ -663,7 +663,7 @@ def constant_items_for_context(context, parent: nil, position:, prefix:, items:)
         if parent
           case parent.type
           when :const
-            const_name = typing.source_index.reference(constant_node: parent)
+            const_name = typing.source_index.reference(constant_node: parent) or raise "Unknown node in source_index: #{parent}"
             consts = context.type_env.constant_env.children(const_name)
           end
         else
diff --git a/lib/steep/type_construction.rb b/lib/steep/type_construction.rb
index e2429da42..332517723 100644
--- a/lib/steep/type_construction.rb
+++ b/lib/steep/type_construction.rb
@@ -2908,6 +2908,8 @@ def type_masgn_type(mlhs_node, rhs_type, masgn:, optional:)
             _, constr = constr.gvasgn(asgn_node, type)
           when :mlhs
             constr = (constr.type_masgn_type(asgn_node, type, masgn: masgn, optional: optional) or return)
+          else
+            _, constr = constr.synthesize_children(asgn_node).add_typing(asgn_node, type: AST::Builtin.any_type)
           end
 
           if node.type == :splat
diff --git a/test/completion_provider_test.rb b/test/completion_provider_test.rb
index 918755195..8fd953ee0 100644
--- a/test/completion_provider_test.rb
+++ b/test/completion_provider_test.rb
@@ -412,6 +412,27 @@ class World
     end
   end
 
+  def test_on_colon2_call_masgn
+    with_checker <<EOF do
+class Hello
+  class World
+  end
+end
+EOF
+      CompletionProvider.new(source_text: <<-EOR, path: Pathname("foo.rb"), subtyping: checker).tap do |provider|
+Hello::
+a, b = []
+      EOR
+
+        provider.run(line: 1, column: 7).tap do |items|
+          items.grep(CompletionProvider::ConstantItem).tap do |items|
+            assert_equal [:World], items.map(&:identifier).sort
+          end
+        end
+      end
+    end
+  end
+
   def test_simple_method_name_item_two_defs
     with_checker <<~RBS do
         class TestClass