diff --git a/prism_compile.c b/prism_compile.c
index 4bcbeb1208..dc2b3387fe 100644
--- a/prism_compile.c
+++ b/prism_compile.c
@@ -2711,6 +2711,7 @@ pm_compile_defined_expr0(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *co
       case PM_CLASS_VARIABLE_OR_WRITE_NODE:
 
       case PM_INDEX_AND_WRITE_NODE:
+      case PM_INDEX_OPERATOR_WRITE_NODE:
 
       case PM_INSTANCE_VARIABLE_WRITE_NODE:
       case PM_INSTANCE_VARIABLE_OPERATOR_WRITE_NODE:
diff --git a/test/ruby/test_compile_prism.rb b/test/ruby/test_compile_prism.rb
index d64cef57d8..def4bd1e26 100644
--- a/test/ruby/test_compile_prism.rb
+++ b/test/ruby/test_compile_prism.rb
@@ -246,6 +246,7 @@ module Prism
       assert_prism_eval("defined?(Prism::CPOrWN ||= 1)")
       assert_prism_eval("defined?(Prism::CPWN = 1)")
       assert_prism_eval("defined?([0][0] &&= 1)")
+      assert_prism_eval("defined?([0][0] += 1)")
     end
 
     def test_GlobalVariableReadNode