diff --git a/harness/harness-common.rb b/harness/harness-common.rb
index 2d9ceb74..096036d0 100644
--- a/harness/harness-common.rb
+++ b/harness/harness-common.rb
@@ -8,7 +8,7 @@
 end
 
 # Support enabling GC auto-compaction via environment variable
-GC.auto_compact = !!ENV["RUBY_GC_AUTO_COMPACT"]
+GC.auto_compact = !!ENV["RUBY_GC_AUTO_COMPACT"] if GC.respond_to?(:auto_compact)
 
 # Seed the global random number generator for repeatability between runs
 Random.srand(1337)