diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -2404,20 +2404,15 @@
         nSleepTime = MAX_SLEEP_TIME;
     }
 
-    if (strWalletPass.length() > 0) {
-        if (!pwallet->Unlock(strWalletPass)) {
-            throw JSONRPCError(
-                RPC_WALLET_PASSPHRASE_INCORRECT,
-                "Error: The wallet passphrase entered was incorrect.");
-        }
-    } else {
-        throw std::runtime_error(RPCHelpMan{
-            "walletpassphrase",
-            "Stores the wallet decryption key in memory for <timeout> seconds.",
-            {
-                {"passphrase", RPCArg::Type::STR, false},
-                {"timeout", RPCArg::Type::NUM, false},
-            }}.ToString());
+    if (strWalletPass.empty()) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER,
+                           "passphrase can not be empty");
+    }
+
+    if (!pwallet->Unlock(strWalletPass)) {
+        throw JSONRPCError(
+            RPC_WALLET_PASSPHRASE_INCORRECT,
+            "Error: The wallet passphrase entered was incorrect.");
     }
 
     pwallet->TopUpKeyPool();
@@ -2482,15 +2477,9 @@
     strNewWalletPass.reserve(100);
     strNewWalletPass = request.params[1].get_str().c_str();
 
-    if (strOldWalletPass.length() < 1 || strNewWalletPass.length() < 1) {
-        throw std::runtime_error(RPCHelpMan{
-            "walletpassphrasechange",
-            "Changes the wallet passphrase from <oldpassphrase> to "
-            "<newpassphrase>.",
-            {
-                {"oldpassphrase", RPCArg::Type::STR, false},
-                {"newpassphrase", RPCArg::Type::STR, false},
-            }}.ToString());
+    if (strOldWalletPass.empty() || strNewWalletPass.empty()) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER,
+                           "passphrase can not be empty");
     }
 
     if (!pwallet->ChangeWalletPassphrase(strOldWalletPass, strNewWalletPass)) {
@@ -2616,13 +2605,9 @@
     strWalletPass.reserve(100);
     strWalletPass = request.params[0].get_str().c_str();
 
-    if (strWalletPass.length() < 1) {
-        throw std::runtime_error(RPCHelpMan{
-            "encryptwallet",
-            "Encrypts the wallet with <passphrase>.",
-            {
-                {"passphrase", RPCArg::Type::STR, false},
-            }}.ToString());
+    if (strWalletPass.empty()) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER,
+                           "passphrase can not be empty");
     }
 
     if (!pwallet->EncryptWallet(strWalletPass)) {
diff --git a/test/functional/wallet_encryption.py b/test/functional/wallet_encryption.py
--- a/test/functional/wallet_encryption.py
+++ b/test/functional/wallet_encryption.py
@@ -33,8 +33,18 @@
         privkey = self.nodes[0].dumpprivkey(address)
         assert_equal(privkey[:1], "c")
         assert_equal(len(privkey), 52)
+        assert_raises_rpc_error(
+            -15, "Error: running with an unencrypted wallet, but walletpassphrase was called",
+            self.nodes[0].walletpassphrase, 'ff', 1)
+        assert_raises_rpc_error(
+            -15,
+            "Error: running with an unencrypted wallet, but walletpassphrasechange was called.",
+            self.nodes[0].walletpassphrasechange, 'ff', 'ff')
 
         # Encrypt the wallet
+        assert_raises_rpc_error(
+            -8, "passphrase can not be empty",
+            self.nodes[0].encryptwallet, '')
         self.nodes[0].encryptwallet(passphrase)
 
         # Check the encrypted wallet is marked as locked on initialization
@@ -44,6 +54,15 @@
         assert_raises_rpc_error(
             -13, "Please enter the wallet passphrase with walletpassphrase first",
             self.nodes[0].dumpprivkey, address)
+        assert_raises_rpc_error(
+            -15, "Error: running with an encrypted wallet, but encryptwallet was called.",
+            self.nodes[0].encryptwallet, 'ff')
+        assert_raises_rpc_error(
+            -8, "passphrase can not be empty",
+            self.nodes[0].walletpassphrase, '', 1)
+        assert_raises_rpc_error(
+            -8, "passphrase can not be empty",
+            self.nodes[0].walletpassphrasechange, '', 'ff')
 
         # Check that walletpassphrase works
         self.nodes[0].walletpassphrase(passphrase, 2)