diff --git a/src/if_ruby.c b/src/if_ruby.c
index 44fd5ee..9343ec8 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -96,6 +96,12 @@
 # define rb_num2int rb_num2int_stub
 #endif
 
+# if defined(DYNAMIC_RUBY_VER) && DYNAMIC_RUBY_VER >= 21
+/* Ruby 2.1 adds new GC called RGenGC and RARRAY_PTR uses
+ * rb_gc_writebarrier_unprotect_promoted if USE_RGENGC  */
+#  define rb_gc_writebarrier_unprotect_promoted rb_gc_writebarrier_unprotect_promoted_stub
+# endif
+
 #include <ruby.h>
 #ifdef RUBY19_OR_LATER
 # include <ruby/encoding.h>
@@ -373,6 +379,10 @@
 static void* (*ruby_process_options)(int, char**);
 # endif
 
+# if defined(USE_RGENGC) && USE_RGENGC
+static void (*dll_rb_gc_writebarrier_unprotect_promoted)(VALUE);
+# endif
+
 # if defined(RUBY19_OR_LATER) && !defined(PROTO)
 SIGNED_VALUE rb_num2long_stub(VALUE x)
 {
@@ -406,6 +416,13 @@
 #  endif
 # endif
 
+# if defined(USE_RGENGC) && USE_RGENGC
+void rb_gc_writebarrier_unprotect_promoted_stub(VALUE obj)
+{
+    return dll_rb_gc_writebarrier_unprotect_promoted(obj);
+}
+# endif
+
 static HINSTANCE hinstRuby = NULL; /* Instance of ruby.dll */
 
 /*
@@ -521,6 +538,9 @@
 #  endif
     {"ruby_init_stack", (RUBY_PROC*)&dll_ruby_init_stack},
 # endif
+# if defined(USE_RGENGC) && USE_RGENGC
+    {"rb_gc_writebarrier_unprotect_promoted", (RUBY_PROC*)&dll_rb_gc_writebarrier_unprotect_promoted},
+# endif
     {"", NULL},
 };