diff --git a/common/node_id.c b/common/node_id.c
index 4998323e2..f98bb8159 100644
--- a/common/node_id.c
+++ b/common/node_id.c
@@ -56,14 +56,16 @@ void fromwire_node_id(const u8 **cursor, size_t *max, struct node_id *id)
 	fromwire(cursor, max, &id->k, sizeof(id->k));
 }
 
+bool dev_towire_allow_invalid_node_id = false;
+
 void towire_node_id(u8 **pptr, const struct node_id *id)
 {
-#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
 	/* Cheap sanity check. For wire fuzzing, we only care about correct
 	 * encoding of node IDs and not whether the IDs are valid, so we disable
 	 * this check while fuzzing. */
-	assert(id->k[0] == 0x2 || id->k[0] == 0x3);
-#endif
+	if (!dev_towire_allow_invalid_node_id)
+		assert(id->k[0] == 0x2 || id->k[0] == 0x3);
+
 	towire(pptr, id->k, sizeof(id->k));
 }
 
diff --git a/common/node_id.h b/common/node_id.h
index 0f943a44a..6b1087ed1 100644
--- a/common/node_id.h
+++ b/common/node_id.h
@@ -48,6 +48,9 @@ static inline int node_id_idx(const struct node_id *id1,
 void towire_node_id(u8 **pptr, const struct node_id *id);
 void fromwire_node_id(const u8 **cursor, size_t *max, struct node_id *id);
 
+/* Fuzzer creates these, so sets this flag to allow it */
+extern bool dev_towire_allow_invalid_node_id;
+
 /* Hash table functions for node ids */
 static inline const struct node_id *node_id_keyof(const struct node_id *id)
 {
diff --git a/tests/fuzz/wire.h b/tests/fuzz/wire.h
index 28a523064..23d1ee1c1 100644
--- a/tests/fuzz/wire.h
+++ b/tests/fuzz/wire.h
@@ -21,7 +21,7 @@ static u8 *prefix_arr(const u8 *data, size_t size, u16 prefix)
 }
 
 /* The init function used by all fuzz-wire-* targets. */
-void init(int *argc, char ***argv) { common_setup("fuzzer"); }
+void init(int *argc, char ***argv) { common_setup("fuzzer"); dev_towire_allow_invalid_node_id = true; }
 
 /* Test that decoding arbitrary data does not crash. Then, if the data was
  * successfully decoded, test that encoding and decoding the message does not