diff --git a/spec/addressable/uri_spec.rb b/spec/addressable/uri_spec.rb
index 9ab8038e..1ea645d6 100644
--- a/spec/addressable/uri_spec.rb
+++ b/spec/addressable/uri_spec.rb
@@ -1061,7 +1061,12 @@ def to_s
   end
 
   it "should not allow destructive operations" do
-    expect { @uri.normalize! }.to raise_error(FrozenError)
+    error = if Gem::Version.new(RUBY_VERSION) < Gem::Version.new("2.5.0")
+              RuntimeError
+            else
+              FrozenError
+            end
+    expect { @uri.normalize! }.to raise_error(error)
   end
 end