--- a/coroutine/copy/Context.h
+++ b/coroutine/copy/Context.h
@@ -13,6 +13,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include <alloca.h>
+#include <sys/types.h>
 
 #define COROUTINE __attribute__((noreturn)) void
 
--- a/configure.ac
+++ b/configure.ac
@@ -2347,7 +2347,10 @@ AS_CASE([$rb_cv_coroutine], [yes|''], [
             rb_cv_coroutine=copy
         ],
         [*], [
-            rb_cv_coroutine=ucontext
+            AC_CHECK_FUNCS([getcontext swapcontext makecontext],
+                [rb_cv_coroutine=ucontext],
+                [rb_cv_coroutine=copy; break]
+            )
         ]
     )
     AC_MSG_RESULT(${rb_cv_coroutine})