diff --git a/smocore/qutex.cpp b/smocore/qutex.cpp
index 68f81af..3fe5c88 100644
--- a/smocore/qutex.cpp
+++ b/smocore/qutex.cpp
@@ -295,14 +295,24 @@ void Qutex::release()
 {
 	lock.acquire();
 
-	isOwned = false;
-	/**	FIXME:
-	 * We need to be able to call this twice or more from the same request.
-	 * We can either add further metadata to this class, or we can force all
-	 * release() calls to be done via the Continuation object, such that it
-	 * can ensure that it doesn't double-release any locks that were released
-	 * early.
+	/**	EXPLAINATION:
+	 * A qutex must not have its release() called when it's not owned. The
+	 * plumbing required to permit that is a bit excessive, and we have
+	 * instrumentation to track early qutex release()ing in
+	 * SerializedAsynchronousContinuation.
 	 */
+	if (!isOwned
+#ifdef CONFIG_ENABLE_DEBUG_LOCKS
+		|| currOwner == nullptr
+#endif
+	)
+	{
+		throw std::runtime_error(
+			std::string(__func__) +
+			": release() called on unowned qutex - this should never happen");
+	}
+
+	isOwned = false;
 #ifdef CONFIG_ENABLE_DEBUG_LOCKS
 	currOwner = nullptr;
 #endif