diff --git a/lib/src/commands.rs b/lib/src/commands.rs
index 075dbe8..e0e4c72 100644
--- a/lib/src/commands.rs
+++ b/lib/src/commands.rs
@@ -332,6 +332,44 @@ impl Command for UnlockCommand {
     }
 }
 
+
+struct LockCommand {}
+impl Command for LockCommand {
+    fn help(&self) -> String {
+        let mut h = vec![];
+        h.push("Lock a wallet that's been temporarily unlocked. You should already have encryption enabled.");
+        h.push("Note 1: This will remove all spending keys from memory. The wallet remains encrypted on disk");
+        h.push("Note 2: If you've forgotten the password, the only way to recover the wallet is to restore");
+        h.push("        from the seed phrase.");
+        h.push("Usage:");
+        h.push("lock");
+        h.push("");
+        h.push("Example:");
+        h.push("lock");
+
+        h.join("\n")
+    }
+
+    fn short_help(&self) -> String {
+        "Lock a wallet that's been temporarily unlocked".to_string()
+    }
+
+    fn exec(&self, args: &[&str], lightclient: &LightClient) -> String {
+        if args.len() != 0 {
+            return self.help();
+        }
+
+        match lightclient.wallet.write().unwrap().lock() {
+            Ok(_)  => object!{ "result" => "success" },
+            Err(e) => object!{
+                "result" => "error",
+                "error"  => e.to_string()
+            }
+        }.pretty(2)
+    }
+}
+
+
 struct SendCommand {}
 impl Command for SendCommand {
     fn help(&self) -> String {
@@ -666,6 +704,7 @@ pub fn get_commands() -> Box<HashMap<String, Box<dyn Command>>> {
     map.insert("encrypt".to_string(),       Box::new(EncryptCommand{}));
     map.insert("decrypt".to_string(),       Box::new(DecryptCommand{}));
     map.insert("unlock".to_string(),        Box::new(UnlockCommand{}));
+    map.insert("lock".to_string(),          Box::new(LockCommand{}));
     map.insert("fixbip39bug".to_string(),   Box::new(FixBip39BugCommand{}));
 
     Box::new(map)
diff --git a/lib/src/lightwallet.rs b/lib/src/lightwallet.rs
index 568ba64..0c4dbed 100644
--- a/lib/src/lightwallet.rs
+++ b/lib/src/lightwallet.rs
@@ -594,8 +594,8 @@ impl LightWallet {
     pub fn encrypt(&mut self, passwd: String) -> io::Result<()> {
         use sodiumoxide::crypto::secretbox;
 
-        if self.encrypted && !self.unlocked {
-            return Err(io::Error::new(ErrorKind::AlreadyExists, "Wallet is already encrypted and locked"));
+        if self.encrypted {
+            return Err(io::Error::new(ErrorKind::AlreadyExists, "Wallet is already encrypted"));
         }
 
         // Get the doublesha256 of the password, which is the right length
@@ -615,6 +615,14 @@ impl LightWallet {
     }
 
     pub fn lock(&mut self) -> io::Result<()> {
+        if !self.encrypted {
+            return Err(io::Error::new(ErrorKind::AlreadyExists, "Wallet is not encrypted"));
+        }
+
+        if !self.unlocked {
+            return Err(io::Error::new(ErrorKind::AlreadyExists, "Wallet is already locked"));
+        }
+
         // Empty the seed and the secret keys
         self.seed.copy_from_slice(&[0u8; 32]);
         self.tkeys = Arc::new(RwLock::new(vec![]));
@@ -3144,6 +3152,10 @@ pub mod tests {
 
         let seed = wallet.seed;
 
+        // Trying to lock a wallet that's not encrpyted is an error
+        assert!(wallet.lock().is_err());
+
+        // Encrypt the wallet
         wallet.encrypt("somepassword".to_string()).unwrap();
 
         // Encrypting an already encrypted wallet should fail
@@ -3188,6 +3200,9 @@ pub mod tests {
         wallet.lock().unwrap();
         wallet.write(&mut vec![]).expect("Serialize wallet");
 
+        // Locking an already locked wallet is an error
+        assert!(wallet.lock().is_err());
+
         // Try from a deserialized, locked wallet
         let mut wallet2 = LightWallet::read(&serialized_data[..], &config).unwrap();
         wallet2.unlock("somepassword".to_string()).unwrap();