diff --git a/api.py b/api.py
index c30edfd..391fdf3 100644
--- a/api.py
+++ b/api.py
@@ -16,9 +16,6 @@
 import mkey
 
 
-class BadInputError(ValueError):
-    pass
-
 app = FastAPI()
 app.mount("/static", StaticFiles(directory="static"), name="static")
 
@@ -26,10 +23,12 @@ async def get_mkey(platform: Optional[str] = None, month: Optional[int] = None,
     generator = mkey.mkey_generator(debug=False)
 
     if platform not in ["RVL", "TWL", "CTR", "WUP", "HAC"]:
-        raise BadInputError(f"{platform} is an invalid platform.")
+        raise mkey.InvalidInputError(f"{platform} is an invalid platform.")
     master_key = None
     try:
         master_key = generator.generate(inquiry=inquiry, month=month, day=day, device=platform, aux=aux)
+    except mkey.InvalidInputError as e:
+        raise mkey.InvalidInputError(str(e))
     except ValueError as e:
         raise ValueError(str(e))
     return str(master_key)
@@ -39,7 +38,7 @@ async def get_mkey(platform: Optional[str] = None, month: Optional[int] = None,
 async def api(platform: Optional[str] = None, month: Optional[int] = None, day: Optional[int] = None, inquiry: Optional[str] = None, aux: Optional[str] = None):
     try:
         ret = await get_mkey(platform, month, day, inquiry, aux)
-    except BadInputError as e:
+    except mkey.InvalidInputError as e:
         raise HTTPException(status_code=400, detail=str(e))
     except ValueError as e:
         raise HTTPException(status_code=500, detail=str(e))
diff --git a/mkey.py b/mkey.py
index ed847a0..be9d74c 100644
--- a/mkey.py
+++ b/mkey.py
@@ -31,6 +31,11 @@
 try: import hexdump
 except ImportError: pass
 
+
+class InvalidInputError(ValueError):
+    pass
+
+
 class mkey_generator():
     __props = {
         "RVL": {
@@ -172,7 +177,7 @@ def _detect_algorithm(self, device, inquiry):
             if "v0" in algorithms:
                 return "v0"
             else:
-                raise ValueError("v0 algorithm not supported by %s." % device)
+                raise InvalidInputError("v0 algorithm not supported by %s." % device)
         elif len(inquiry) == 10:
             version = int((int(inquiry) / 10000000) % 100)
 
@@ -183,14 +188,14 @@ def _detect_algorithm(self, device, inquiry):
             elif "v3" in algorithms:
                 return "v3"
             else:
-                raise ValueError("v1/v2/v3 algorithms not supported by %s." % device)
+                raise InvalidInputError("v1/v2/v3 algorithms not supported by %s." % device)
         elif len(inquiry) == 6:
             if "v4" in algorithms:
                 return "v4"
             else:
-                raise ValueError("v4 algorithm not supported by %s." % device)
+                raise InvalidInputError("v4 algorithm not supported by %s." % device)
         else:
-            raise ValueError("Inquiry number must be 6, 8 or 10 digits.")
+            raise InvalidInputError("Inquiry number must be 6, 8 or 10 digits.")
 
     # CRC-32 implementation (v0).
     def _calculate_crc(self, poly, xorout, addout, inbuf):
@@ -260,7 +265,7 @@ def _generate_v1_v2(self, props, inquiry, month, day):
         # be a guaranteed set of regions available.
         #
         if region not in props["regions"]:
-            raise ValueError("%s is an invalid region for console %s." %
+            raise InvalidInputError("%s is an invalid region for console %s." %
                 (region, props["device"]))
 
         #
@@ -373,10 +378,10 @@ def _generate_v3_v4(self, props, inquiry, aux = None):
             raise ValueError("v3/v4 attempted, but data directory doesn't exist or was not specified.")
 
         if algorithm == "v4" and not aux:
-            raise ValueError("v4 attempted, but no auxiliary string (device ID required).")
+            raise InvalidInputError("v4 attempted, but no auxiliary string (device ID required).")
 
         if algorithm == "v4" and len(aux) != 16:
-            raise ValueError("v4 attempted, but auxiliary string (device ID) of invalid length.")
+            raise InvalidInputError("v4 attempted, but auxiliary string (device ID) of invalid length.")
 
         if algorithm == "v4":
             version = int((inquiry / 10000) % 100)
@@ -440,7 +445,7 @@ def _generate_v3_v4(self, props, inquiry, aux = None):
     def generate(self, inquiry, month = None, day = None, aux = None, device = None):
         inquiry = inquiry.replace(" ", "")
         if not inquiry.isdigit():
-            raise ValueError("Inquiry string must represent a decimal number.")
+            raise InvalidInputError("Inquiry string must represent a decimal number.")
 
         if month is None:
             month = datetime.date.today().month
@@ -448,14 +453,14 @@ def generate(self, inquiry, month = None, day = None, aux = None, device = None)
             day = datetime.date.today().day
 
         if month < 1 or month > 12:
-            raise ValueError("Month must be between 1 and 12.")
+            raise InvalidInputError("Month must be between 1 and 12.")
 
         if day < 1 or day > 31:
-            raise ValueError("Day must be between 1 and 31.")
+            raise InvalidInputError("Day must be between 1 and 31.")
 
         if not device: device = self.default_device
         if device not in self.devices:
-            raise ValueError("Unsupported device: %s." % device)
+            raise InvalidInputError("Unsupported device: %s." % device)
 
         # We can glean information about the required algorithm from the inquiry number.
         algorithm = self._detect_algorithm(device, inquiry)