diff --git a/src/ssb.js.c b/src/ssb.js.c
index a9b48e6f..ab7bb90c 100644
--- a/src/ssb.js.c
+++ b/src/ssb.js.c
@@ -2239,53 +2239,60 @@ static void _tf_ssb_private_message_decrypt_work(tf_ssb_t* ssb, void* user_data)
 
 	if (found)
 	{
-		uint8_t* decoded = tf_malloc(work->message_size);
-		int decoded_length = tf_base64_decode(work->message, work->message_size - strlen(".box"), decoded, work->message_size);
-		uint8_t* nonce = decoded;
-		uint8_t* public_key = decoded + crypto_box_NONCEBYTES;
-		if (public_key + crypto_secretbox_KEYBYTES < decoded + decoded_length)
+		if (work->message_size >= strlen(".box") && memcmp(work->message + work->message_size - strlen(".box"), ".box", strlen(".box")) == 0)
 		{
-			uint8_t shared_secret[crypto_secretbox_KEYBYTES] = { 0 };
-			if (crypto_scalarmult(shared_secret, private_key, public_key) == 0)
+			uint8_t* decoded = tf_malloc(work->message_size);
+			int decoded_length = tf_base64_decode(work->message, work->message_size - strlen(".box"), decoded, work->message_size);
+			uint8_t* nonce = decoded;
+			uint8_t* public_key = decoded + crypto_box_NONCEBYTES;
+			if (public_key + crypto_secretbox_KEYBYTES < decoded + decoded_length)
 			{
-				enum
+				uint8_t shared_secret[crypto_secretbox_KEYBYTES] = { 0 };
+				if (crypto_scalarmult(shared_secret, private_key, public_key) == 0)
 				{
-					k_recipient_header_bytes = crypto_secretbox_MACBYTES + sizeof(uint8_t) + crypto_secretbox_KEYBYTES
-				};
-				for (uint8_t* p = decoded + crypto_box_NONCEBYTES + crypto_secretbox_KEYBYTES; p <= decoded + decoded_length - k_recipient_header_bytes;
-					 p += k_recipient_header_bytes)
-				{
-					uint8_t out[k_recipient_header_bytes] = { 0 };
-					int opened = crypto_secretbox_open_easy(out, p, k_recipient_header_bytes, nonce, shared_secret);
-					if (opened != -1)
+					enum
 					{
-						int recipients = (int)out[0];
-						uint8_t* body = decoded + crypto_box_NONCEBYTES + crypto_secretbox_KEYBYTES + k_recipient_header_bytes * recipients;
-						size_t body_size = decoded + decoded_length - body;
-						uint8_t* decrypted = tf_malloc(body_size);
-						uint8_t* key = out + 1;
-						if (crypto_secretbox_open_easy(decrypted, body, body_size, nonce, key) != -1)
+						k_recipient_header_bytes = crypto_secretbox_MACBYTES + sizeof(uint8_t) + crypto_secretbox_KEYBYTES
+					};
+					for (uint8_t* p = decoded + crypto_box_NONCEBYTES + crypto_secretbox_KEYBYTES; p <= decoded + decoded_length - k_recipient_header_bytes;
+						 p += k_recipient_header_bytes)
+					{
+						uint8_t out[k_recipient_header_bytes] = { 0 };
+						int opened = crypto_secretbox_open_easy(out, p, k_recipient_header_bytes, nonce, shared_secret);
+						if (opened != -1)
 						{
-							work->decrypted = (const char*)decrypted;
-							work->decrypted_size = body_size - crypto_secretbox_MACBYTES;
-						}
-						else
-						{
-							work->error = "Received key to open secret box containing message body, but it did not work.";
+							int recipients = (int)out[0];
+							uint8_t* body = decoded + crypto_box_NONCEBYTES + crypto_secretbox_KEYBYTES + k_recipient_header_bytes * recipients;
+							size_t body_size = decoded + decoded_length - body;
+							uint8_t* decrypted = tf_malloc(body_size);
+							uint8_t* key = out + 1;
+							if (crypto_secretbox_open_easy(decrypted, body, body_size, nonce, key) != -1)
+							{
+								work->decrypted = (const char*)decrypted;
+								work->decrypted_size = body_size - crypto_secretbox_MACBYTES;
+							}
+							else
+							{
+								work->error = "Received key to open secret box containing message body, but it did not work.";
+							}
 						}
 					}
 				}
+				else
+				{
+					work->error = "crypto_scalarmult failed.";
+				}
 			}
 			else
 			{
-				work->error = "crypto_scalarmult failed.";
+				work->error = "Encrypted message was not long enough to contain its one-time public key.";
 			}
+			tf_free(decoded);
 		}
 		else
 		{
-			work->error = "Encrypted message was not long enough to contains its one-time public key.";
+			work->error = "Message does not end in \".box\".";
 		}
-		tf_free(decoded);
 	}
 	else
 	{