diff --git a/wrappers/libnimbus.h b/wrappers/libnimbus.h
index 5d7926eac..350323ad5 100644
--- a/wrappers/libnimbus.h
+++ b/wrappers/libnimbus.h
@@ -12,8 +12,8 @@ extern "C" {
 typedef struct {
   uint8_t* decoded;
   size_t decodedLen;
-  uint8_t source[64]; /* TODO: change to ptr so they can be checked on nil? */
-  uint8_t recipientPublicKey[64]; /* TODO: change to ptr so they can be checked on nil? */
+  uint8_t* source; /* 64 bytes public key, can be nil */
+  uint8_t* recipientPublicKey; /* 64 bytes public key, can be nil */
   uint32_t timestamp;
   uint32_t ttl;
   uint8_t topic[4];
@@ -22,11 +22,11 @@ typedef struct {
 } received_message;
 
 typedef struct {
-  const char* symKeyID;
-  const char* privateKeyID;
-  uint8_t* source; /* 64 bytes public key */
+  const char* symKeyID; /* Identifier for symmetric key, set to nil if none */
+  const char* privateKeyID; /* Identifier for asymmetric key, set to nil if none */
+  uint8_t* source; /* 64 bytes public key, set to nil if none */
   double minPow;
-  uint8_t topic[4];
+  uint8_t topic[4]; /* Will default to 0x00000000 if not provided */
   int allowP2P;
 } filter_options;
 
@@ -35,10 +35,10 @@ typedef struct {
   uint8_t* pubKey; /* 64 bytes public key, set to nil if none */
   const char* sourceID; /* Identifier for asymmetric key, set to nil if none */
   uint32_t ttl;
-  uint8_t topic[4]; /* default of 0 is OK */
-  uint8_t* payload; /* payload to be send, can be len=0 but can not be nil */
+  uint8_t topic[4]; /* Will default to 0x00000000 if not provided */
+  uint8_t* payload; /* Payload to be send, can be len=0 but can not be nil */
   size_t payloadLen;
-  uint8_t* padding; /* custom padding, can be set to nil */
+  uint8_t* padding; /* Custom padding, can be set to nil */
   size_t paddingLen;
   double powTime;
   double powTarget;
diff --git a/wrappers/libnimbus.nim b/wrappers/libnimbus.nim
index ee2ed61bf..fa16b2b29 100644
--- a/wrappers/libnimbus.nim
+++ b/wrappers/libnimbus.nim
@@ -31,8 +31,8 @@ type
   CReceivedMessage* = object
     decoded*: ptr byte
     decodedLen*: csize
-    source*: PublicKey
-    recipientPublicKey*: PublicKey
+    source*: ref PublicKey
+    recipientPublicKey*: ref PublicKey
     timestamp*: uint32
     ttl*: uint32
     topic*: Topic
@@ -430,11 +430,18 @@ proc nimbus_subscribe_filter(options: ptr CFilterOptions,
         hash: msg.hash
       )
 
-      # TODO: change this to ptr, so that C/go code can check on nil?
+      # Should be GCed when handler goes out of scope
+      var
+        source: ref PublicKey
+        recipientPublicKey: ref PublicKey
       if msg.decoded.src.isSome():
-        cmsg.source = msg.decoded.src.get()
+        new(source)
+        source[] = msg.decoded.src.get()
+        cmsg.source = source
       if msg.dst.isSome():
-        cmsg.recipientPublicKey = msg.dst.get()
+        new(recipientPublicKey)
+        recipientPublicKey[] = msg.dst.get()
+        cmsg.recipientPublicKey = recipientPublicKey
 
       handler(addr cmsg, udata)
 
diff --git a/wrappers/wrapper_whisper_example.go b/wrappers/wrapper_whisper_example.go
index da7d272ea..cb5975750 100644
--- a/wrappers/wrapper_whisper_example.go
+++ b/wrappers/wrapper_whisper_example.go
@@ -37,7 +37,10 @@ func poll() {
 func receiveHandler(msg *C.received_message, udata unsafe.Pointer) {
 	receivedMsg := C.GoBytes(unsafe.Pointer(msg.decoded), C.int(msg.decodedLen))
 	fmt.Printf("[nim-status] received message %s\n", string(receivedMsg))
-	fmt.Printf("[nim-status] source public key %x\n", msg.source)
+	if msg.source != nil {
+		source := C.GoBytes(unsafe.Pointer(msg.source), 64)
+		fmt.Printf("[nim-status] source public key %x\n", string(source))
+	}
 	msgCount := (*int)(udata)
 	*msgCount += 1
 	fmt.Printf("[nim-status] message count %d\n", *msgCount)