diff --git a/src/core/operations/SeedToMPK.mjs b/src/core/operations/SeedToMPK.mjs
index fc7aafb0..23f6f878 100644
--- a/src/core/operations/SeedToMPK.mjs
+++ b/src/core/operations/SeedToMPK.mjs
@@ -48,16 +48,17 @@ class SeedToMPK extends Operation {
             return "";
         }
         input = input.trim();
+
+
         // We check to see if the input is hex or not.
         // If it is not, we convert it back to hex
-        const re = /[0-9A-Fa-f]{2,}/g;
-        if (!(input.length === 128 && re.test(input)) && !(input.length === 64)) {
-            return "Must pass a hex string of length 128, or a byte string of length 64. Got length: " + input.length;
-        }
+        const re = /^[0-9A-Fa-f]{2,}$/g;
+        const isHex = re.test(input) && input.length %2 === 0;
 
+        // Create the hmac.
         const hmac = forge.hmac.create();
         hmac.start("sha512", Utils.convertToByteString("Bitcoin seed", "UTF8"));
-        if (input.length === 128) {
+        if (isHex) {
             hmac.update(Utils.convertToByteString(input, "hex"));
         } else {
             hmac.update(input);
diff --git a/tests/operations/tests/SeedToMPK.mjs b/tests/operations/tests/SeedToMPK.mjs
index 00e3e586..9bf84c36 100644
--- a/tests/operations/tests/SeedToMPK.mjs
+++ b/tests/operations/tests/SeedToMPK.mjs
@@ -57,6 +57,49 @@ TestRegister.addTests([
                 "args": ["Ltpv"]
             }
         ],
+    },
+    {
+        name: "Seed To Master Private Key (XPrv, short seed)",
+        input: "1ed5b6f0dcf88085add90fbb138d5e16f661d5b738f842232fce5980fc4592",
+        expectedOutput: "xprv9s21ZrQH143K3mvkwf3aiiCQ6mpTnAh5ZPvhHFLXSaSRxAg5uAuHVvaFVSGoyE7U3UJ3knZM12AvNcF9a9xoARWCkCF9MYXjyN1ZJUC6ssa",
+        recipeConfig: [
+            {
+                "op": "Seed To Master Key",
+                "args": ["xprv"]
+            }
+        ],
+    },
+    {
+        name: "Seed to Master Private Key (XPrv, decoded Chinese)",
+        input: "霍 里 攻 繁 混 注 杀 侦 具 涤 涤 手",
+        expectedOutput: "xprv9s21ZrQH143K3NGAQKJovUKk9ty8HFDxoK2A8kseKUEQnQA2xuS1UiXj67d7jPS153aBSeqbJpGC4etDSmAJrD2MuN3pncdjFNh85PEPwS2",
+        recipeConfig: [
+            {
+                "op": "Normalise Unicode",
+                "args": ["NFKD"]
+            },
+            {
+                "op": "To Hex",
+                "args": ["None", 0]
+            },
+            {
+                "op": "Seed To Master Key",
+                "args": ["xprv"]
+            }
+
+        ]
+    },
+    {
+        name: "Seed to Master Private Key (XPrv, Non-Hex Dealing With Raw Bytes)",
+        input: "abc=_*~$%^$^*&^$%@#$^^%&*^&(YIU%^$#@",
+        expectedOutput: "xprv9s21ZrQH143K2zVX3HhaQJZPeunqrxitrCQh5ZaUzyv9uHtZu86AVigehGy2ZCfGcAmp7wJUSb4GMGsbH8qqJawZEz2mdUVV8q7VH2AqgH6",
+        recipeConfig: [
+            {
+                "op": "Seed To Master Key",
+                "args": ["xprv"]
+            }
+
+        ]
     }
 
 ]);