diff --git a/lib/method_source.rb b/lib/method_source.rb
index ffd79ad..d6fa7fa 100644
--- a/lib/method_source.rb
+++ b/lib/method_source.rb
@@ -152,6 +152,10 @@ def class_comment
         class_inst_or_module = class_inst_or_module.class
       end
 
+      unless const_name
+        raise SourceNotFoundError, "Could not locate source for an anonymous class or module!"
+      end
+
       location = class_inst_or_module.const_source_location(const_name)
 
       MethodSource.comment_helper(location, defined?(name) ? name : inspect)
@@ -174,4 +178,3 @@ class Proc
   include MethodSource::SourceLocation::ProcExtensions
   include MethodSource::MethodExtensions
 end
-
diff --git a/spec/method_source_spec.rb b/spec/method_source_spec.rb
index 1927670..030f61f 100644
--- a/spec/method_source_spec.rb
+++ b/spec/method_source_spec.rb
@@ -123,6 +123,16 @@
     it 'should return comment for class instance' do
       expect(C.new.method(:hello).class_comment).to eq(@class_comment)
     end
+
+    it 'should raise a source error for an anonymous class' do
+      anonymous_class = Class.new do
+        def hello; end
+      end
+
+      expect do
+        anonymous_class.instance_method(:hello).class_comment
+      end.to raise_error(MethodSource::SourceNotFoundError, /anonymous class/)
+    end
   end
   # end
   describe "Comment tests" do