diff --git a/ql/src/codeql_ruby/ast/Call.qll b/ql/src/codeql_ruby/ast/Call.qll
index bc2231d94f3..e301a1b5b9d 100644
--- a/ql/src/codeql_ruby/ast/Call.qll
+++ b/ql/src/codeql_ruby/ast/Call.qll
@@ -162,6 +162,9 @@ private class RegularMethodCall extends MethodCall, TRegularMethodCall {
     not exists(g.getReceiver()) and
     toGenerated(result) = g.getMethod().(Generated::ScopeResolution).getScope()
     or
+    // If there's no explicit receiver (or scope resolution that acts like a
+    // receiver), then the receiver is implicitly `self`.  N.B.  `::Foo()` is
+    // not valid Ruby.
     not exists(g.getReceiver()) and
     not exists(g.getMethod().(Generated::ScopeResolution).getScope()) and
     result = TRegularMethodCallImplicitSelf(g)