diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 5d0fc85baa..380015248b 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -128,6 +128,30 @@ rb_rational_den(VALUE rat)
 }
 #endif
 
+#ifndef HAVE_RB_COMPLEX_REAL
+static inline VALUE
+rb_complex_real(VALUE cmp)
+{
+#ifdef HAVE_TYPE_STRUCT_RCOMPLEX
+  return RCOMPLEX(cmp)->real;
+#else
+  return rb_funcall(cmp, rb_intern("real"), 0);
+#endif
+}
+#endif
+
+#ifndef HAVE_RB_COMPLEX_IMAG
+static inline VALUE
+rb_complex_imag(VALUE cmp)
+{
+#ifdef HAVE_TYPE_STRUCT_RCOMPLEX
+  return RCOMPLEX(cmp)->imag;
+#else
+  return rb_funcall(cmp, rb_intern("imag"), 0);
+#endif
+}
+#endif
+
 #define BIGDECIMAL_POSITIVE_P(bd) ((bd)->sign > 0)
 #define BIGDECIMAL_NEGATIVE_P(bd) ((bd)->sign < 0)
 
diff --git a/ext/bigdecimal/extconf.rb b/ext/bigdecimal/extconf.rb
index b4098fdacf..fc448ed380 100644
--- a/ext/bigdecimal/extconf.rb
+++ b/ext/bigdecimal/extconf.rb
@@ -36,6 +36,9 @@ have_func("isfinite", "math.h")
 have_type("struct RRational", "ruby.h")
 have_func("rb_rational_num", "ruby.h")
 have_func("rb_rational_den", "ruby.h")
+have_type("struct RComplex", "ruby.h")
+have_func("rb_complex_real", "ruby.h")
+have_func("rb_complex_imag", "ruby.h")
 have_func("rb_array_const_ptr", "ruby.h")
 have_func("rb_sym2str", "ruby.h")
 have_func("rb_opts_exception_p", "ruby.h")