diff --git a/common/node_id.h b/common/node_id.h
index 1f23c9d33..1e2f8d063 100644
--- a/common/node_id.h
+++ b/common/node_id.h
@@ -3,6 +3,9 @@
 #define LIGHTNING_COMMON_NODE_ID_H
 #include "config.h"
 #include <bitcoin/pubkey.h>
+#include <ccan/crypto/siphash24/siphash24.h>
+#include <ccan/htable/htable_type.h>
+#include <common/pseudorand.h>
 
 struct node_id {
 	u8 k[PUBKEY_CMPR_LEN];
@@ -43,4 +46,21 @@ static inline int node_id_idx(const struct node_id *id1,
 /* marshal/unmarshal functions */
 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);
+
+/* Hash table functions for node ids */
+static inline const struct node_id *node_id_keyof(const struct node_id *id)
+{
+	return id;
+}
+
+/* We need to define a hashing function. siphash24 is a fast yet
+ * cryptographic hash in ccan/crypto/siphash24; we might be able to get away
+ * with a slightly faster hash with fewer guarantees, but it's good hygiene to
+ * use this unless it's a proven bottleneck.  siphash_seed() is a function in
+ * common/pseudorand which sets up a seed for our hashing; it's different
+ * every time the program is run. */
+static inline size_t node_id_hash(const struct node_id *id)
+{
+	return siphash24(siphash_seed(), id->k, sizeof(id->k));
+}
 #endif /* LIGHTNING_COMMON_NODE_ID_H */
diff --git a/connectd/connectd.h b/connectd/connectd.h
index c94088745..8a35a02b8 100644
--- a/connectd/connectd.h
+++ b/connectd/connectd.h
@@ -100,16 +100,8 @@ static const struct node_id *peer_keyof(const struct peer *peer)
 	return &peer->id;
 }
 
-/*~ We also need to define a hashing function. siphash24 is a fast yet
- * cryptographic hash in ccan/crypto/siphash24; we might be able to get away
- * with a slightly faster hash with fewer guarantees, but it's good hygiene to
- * use this unless it's a proven bottleneck.  siphash_seed() is a function in
- * common/pseudorand which sets up a seed for our hashing; it's different
- * every time the program is run. */
-static size_t node_id_hash(const struct node_id *id)
-{
-	return siphash24(siphash_seed(), id->k, sizeof(id->k));
-}
+/*~ We reuse node_id_hash from common/node_id.h, which uses siphash
+ * and a per-run seed. */
 
 /*~ We also define an equality function: is this element equal to this key? */
 static bool peer_eq_node_id(const struct peer *peer,
diff --git a/lightningd/log.c b/lightningd/log.c
index ff7f1602e..85b450a42 100644
--- a/lightningd/log.c
+++ b/lightningd/log.c
@@ -98,11 +98,6 @@ static const struct node_id *node_cache_id(const struct node_id_cache *nc)
 	return &nc->node_id;
 }
 
-static size_t node_id_hash(const struct node_id *id)
-{
-	return siphash24(siphash_seed(), id->k, sizeof(id->k));
-}
-
 static bool node_id_cache_eq(const struct node_id_cache *nc,
 			     const struct node_id *node_id)
 {
diff --git a/plugins/topology.c b/plugins/topology.c
index 510a7901a..943dcd54d 100644
--- a/plugins/topology.c
+++ b/plugins/topology.c
@@ -192,17 +192,6 @@ static struct command_result *json_getroute(struct command *cmd,
 	return command_finished(cmd, js);
 }
 
-static const struct node_id *node_id_keyof(const struct node_id *id)
-{
-	return id;
-}
-
-static size_t node_id_hash(const struct node_id *id)
-{
-	return siphash24(siphash_seed(), id->k, sizeof(id->k));
-}
-
-
 HTABLE_DEFINE_TYPE(struct node_id, node_id_keyof, node_id_hash, node_id_eq,
 		   node_map);