diff --git a/lib/cext/ABI_check.txt b/lib/cext/ABI_check.txt
index b6a7d89c68e0..98d9bcb75a68 100644
--- a/lib/cext/ABI_check.txt
+++ b/lib/cext/ABI_check.txt
@@ -1 +1 @@
-16
+17
diff --git a/lib/truffle/truffle/cext.rb b/lib/truffle/truffle/cext.rb
index 8cd2a3c01583..2b19e6332641 100644
--- a/lib/truffle/truffle/cext.rb
+++ b/lib/truffle/truffle/cext.rb
@@ -603,6 +603,10 @@ def rb_class_real(ruby_class)
     ruby_class
   end
 
+  def rb_class_get_superclass(ruby_class)
+    ruby_class.superclass || false
+  end
+
   def rb_obj_respond_to(object, name, priv)
     object.respond_to?(name, priv != 0)
   end
diff --git a/src/main/c/cext/class.c b/src/main/c/cext/class.c
index ee23e0d1a8e3..33317b067878 100644
--- a/src/main/c/cext/class.c
+++ b/src/main/c/cext/class.c
@@ -51,6 +51,10 @@ VALUE rb_singleton_class(VALUE object) {
   return RUBY_CEXT_INVOKE("rb_singleton_class", object);
 }
 
+VALUE rb_class_get_superclass(VALUE klass) {
+  return RUBY_CEXT_INVOKE("rb_class_get_superclass", klass);
+}
+
 VALUE rb_obj_alloc(VALUE ruby_class) {
   return RUBY_INVOKE(ruby_class, "__allocate__");
 }