diff --git a/adb/adb_auth.cpp b/adb/adb_auth.cpp
index 33da4bd..0b07158 100644
--- a/adb/adb_auth.cpp
+++ b/adb/adb_auth.cpp
@@ -64,7 +64,9 @@
 
     p->msg.command = A_AUTH;
     p->msg.arg0 = ADB_AUTH_RSAPUBLICKEY;
-    p->msg.data_length = key.size();
+
+    // adbd expects a null-terminated string.
+    p->msg.data_length = key.size() + 1;
     send_packet(p, t);
 }