diff --git a/ext/-test-/cxxanyargs/extconf.rb b/ext/-test-/cxxanyargs/extconf.rb
index 08d8c83010..f128984522 100644
--- a/ext/-test-/cxxanyargs/extconf.rb
+++ b/ext/-test-/cxxanyargs/extconf.rb
@@ -2,12 +2,19 @@
 
 cxx = MakeMakefile["C++"]
 
+# #### have_devel hack ####
+# cxx.try_compile tries to detect compilers, but the try_compile below is
+# trying to detect a compiler in a different way.  We need to prevent the
+# default detection routine.
+
+cxx.instance_variable_set(:'@have_devel', true)
+
 ok = cxx.try_compile(<<~'begin', "") do |x|
   #include "ruby/config.h"
 
   namespace {
-      typedef int conftest[SIZEOF_LONG == sizeof(long) ? 1 : -1];
-      typedef int conftest[SIZEOF_VOIDP == sizeof(void*) ? 1 : -1];
+      typedef int conftest1[SIZEOF_LONG == sizeof(long) ? 1 : -1];
+      typedef int conftest2[SIZEOF_VOIDP == sizeof(void*) ? 1 : -1];
   }
 
   int
@@ -21,6 +28,8 @@ begin
   x.sub! %<#include "ruby.h">, ''
 end
 
+cxx.instance_variable_set(:'@have_devel', ok)
+
 if ok
   $srcs = %w[cxxanyargs.cpp]
   failures = Dir.glob($srcdir + "/failure*.cpp").map {|n| File.basename(n)}