diff --git a/prism_compile.c b/prism_compile.c
index 5b30895fc6..951630c265 100644
--- a/prism_compile.c
+++ b/prism_compile.c
@@ -1491,6 +1491,7 @@ pm_compile_defined_expr0(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *co
       case PM_OR_NODE:
       case PM_RANGE_NODE:
       case PM_REGULAR_EXPRESSION_NODE:
+      case PM_SOURCE_ENCODING_NODE:
       case PM_STRING_NODE:
       case PM_SYMBOL_NODE:
       case PM_X_STRING_NODE:
diff --git a/test/ruby/test_compile_prism.rb b/test/ruby/test_compile_prism.rb
index f2962dc3c7..3cad58a184 100644
--- a/test/ruby/test_compile_prism.rb
+++ b/test/ruby/test_compile_prism.rb
@@ -110,6 +110,7 @@ module Prism
       assert_prism_eval("defined? -> { 1 + 1 }")
       assert_prism_eval("defined? a && b")
       assert_prism_eval("defined? a || b")
+      assert_prism_eval("defined? __ENCODING__")
 
       assert_prism_eval("defined? %[1,2,3]")
       assert_prism_eval("defined? %q[1,2,3]")