diff --git a/eval.c b/eval.c
index b6fedf11f36702..0f56d8eaec0c39 100644
--- a/eval.c
+++ b/eval.c
@@ -1492,12 +1492,6 @@ rb_using_module(const rb_cref_t *cref, VALUE module)
     rb_clear_all_refinement_method_cache();
 }
 
-void
-rb_vm_using_module(VALUE module)
-{
-    rb_using_module(rb_vm_cref_replace_with_duplicated_cref(), module);
-}
-
 /*
  *  call-seq:
  *     target    -> class_or_module
diff --git a/internal/eval.h b/internal/eval.h
index 17ade0a7f1e667..3f6b62d8fe5341 100644
--- a/internal/eval.h
+++ b/internal/eval.h
@@ -29,7 +29,6 @@ void rb_class_modify_check(VALUE);
 NORETURN(VALUE rb_f_raise(int argc, VALUE *argv));
 VALUE rb_exception_setup(int argc, VALUE *argv);
 void rb_refinement_setup(struct rb_refinements_data *data, VALUE module, VALUE klass);
-void rb_vm_using_module(VALUE module);
 VALUE rb_top_main_class(const char *method);
 VALUE rb_ec_ensure(rb_execution_context_t *ec, VALUE (*b_proc)(VALUE), VALUE data1, VALUE (*e_proc)(VALUE), VALUE data2);
 
diff --git a/process.c b/process.c
index ebc73ff07ae6bc..01aea3239a3696 100644
--- a/process.c
+++ b/process.c
@@ -1673,18 +1673,6 @@ proc_exec_sh(const char *str, VALUE envp_str)
 
 #ifdef _WIN32
     rb_w32_uspawn(P_OVERLAY, (char *)str, 0);
-#elif defined(__CYGWIN32__)
-    {
-        char fbuf[MAXPATHLEN];
-        char *shell = dln_find_exe_r("sh", 0, fbuf, sizeof(fbuf));
-        int status = -1;
-        if (shell)
-            execl(shell, "sh", "-c", str, (char *) NULL);
-        else
-            status = system(str);
-        if (status != -1)
-            exit(status);
-    }
 #else
     if (envp_str)
         execle("/bin/sh", "sh", "-c", str, (char *)NULL, RB_IMEMO_TMPBUF_PTR(envp_str)); /* async-signal-safe */