diff --git a/tests/qtest/fuzz/fuzz.h b/tests/qtest/fuzz/fuzz.h
index ed9ce17154..08e9560a79 100644
--- a/tests/qtest/fuzz/fuzz.h
+++ b/tests/qtest/fuzz/fuzz.h
@@ -100,6 +100,7 @@ typedef struct FuzzTarget {
                        uint8_t *out, size_t max_out_size,
                        unsigned int seed);
 
+    void *opaque;
 } FuzzTarget;
 
 void flush_events(QTestState *);