diff --git a/siwe/defs.py b/siwe/defs.py
index adf28fc..c1442b8 100644
--- a/siwe/defs.py
+++ b/siwe/defs.py
@@ -1,5 +1,6 @@
 """Regexes for the various fields."""
 
+SCHEME = "((?P<scheme>([a-zA-Z][a-zA-Z0-9\\+\\-\\.]*))://)?"
 DOMAIN = "(?P<domain>([^/?#]+)) wants you to sign in with your Ethereum account:\\n"
 ADDRESS = "(?P<address>0x[a-zA-Z0-9]{40})\\n\\n"
 STATEMENT = "((?P<statement>[^\\n]+)\\n)?\\n"
@@ -19,6 +20,6 @@
 REQUEST_ID = "(\\nRequest ID: (?P<requestId>[-._~!$&'()*+,;=:@%a-zA-Z0-9]*))?"
 RESOURCES = f"(\\nResources:(?P<resources>(\\n- {URI})+))?"
 REGEX_MESSAGE = (
-    f"^{DOMAIN}{ADDRESS}{STATEMENT}{URI_LINE}{VERSION}{CHAIN_ID}{NONCE}"
+    f"^{SCHEME}{DOMAIN}{ADDRESS}{STATEMENT}{URI_LINE}{VERSION}{CHAIN_ID}{NONCE}"
     f"{ISSUED_AT}{EXPIRATION_TIME}{NOT_BEFORE}{REQUEST_ID}{RESOURCES}$"
 )
diff --git a/siwe/grammars/eip4361.py b/siwe/grammars/eip4361.py
index 3e37eac..1d76ac7 100644
--- a/siwe/grammars/eip4361.py
+++ b/siwe/grammars/eip4361.py
@@ -14,6 +14,7 @@
         # RFC 3986
         ("URI", rfc3986.Rule("URI")),
         ("authority", rfc3986.Rule("authority")),
+        ("scheme", rfc3986.Rule("scheme")),
         ("reserved", rfc3986.Rule("reserved")),
         ("unreserved", rfc3986.Rule("unreserved")),
         ("reserved", rfc3986.Rule("reserved")),
@@ -31,12 +32,12 @@ class Rule(_Rule):
     """Rules from EIP-4361."""
 
     grammar: ClassVar[List] = [
-        'sign-in-with-ethereum = domain %s" wants you to sign in with your Ethereum '
-        'account:" LF address LF LF [ statement LF ] LF %s"URI: " uri LF %s"Version: "'
-        ' version LF %s"Chain ID: " chain-id LF %s"Nonce: " nonce LF %s"Issued At: " '
-        'issued-at [ LF %s"Expiration Time: " expiration-time ] [ LF %s"Not Before: " '
-        'not-before ] [ LF %s"Request ID: " request-id ] [ LF %s"Resources:" resources '
-        "]",
+        'sign-in-with-ethereum = [ scheme "://" ] domain %s" wants you to sign in with '
+        'your Ethereum account:" LF address LF LF [ statement LF ] LF %s"URI: " uri LF '
+        '%s"Version: " version LF %s"Chain ID: " chain-id LF %s"Nonce: " nonce LF %s"'
+        'Issued At: " issued-at [ LF %s"Expiration Time: " expiration-time ] [ LF %s"'
+        'Not Before: " not-before ] [ LF %s"Request ID: " request-id ] [ LF %s"'
+        'Resources:" resources ]',
         "domain = authority",
         'address = "0x" 40HEXDIG',
         'statement = 1*( reserved / unreserved / " " )',
diff --git a/siwe/parsed.py b/siwe/parsed.py
index ca9311f..5c78fd2 100644
--- a/siwe/parsed.py
+++ b/siwe/parsed.py
@@ -20,6 +20,7 @@ def __init__(self, message: str):
             raise ValueError("Message did not match the regular expression.")
 
         self.match = match
+        self.scheme = match.group(expr.groupindex["scheme"])
         self.domain = match.group(expr.groupindex["domain"])
         self.address = match.group(expr.groupindex["address"])
         self.statement = match.group(expr.groupindex["statement"])
@@ -49,6 +50,7 @@ def __init__(self, message: str):
 
         for child in node.children:
             if child.name in [
+                "scheme",
                 "domain",
                 "address",
                 "statement",
diff --git a/siwe/siwe.py b/siwe/siwe.py
index a2b5ac7..2442016 100644
--- a/siwe/siwe.py
+++ b/siwe/siwe.py
@@ -72,6 +72,12 @@ class NotYetValidMessage(VerificationError):
     pass
 
 
+class SchemeMismatch(VerificationError):
+    """The message does not contain the expected scheme."""
+
+    pass
+
+
 class DomainMismatch(VerificationError):
     """The message does not contain the expected domain."""
 
@@ -157,6 +163,8 @@ def utc_now() -> datetime:
 class SiweMessage(BaseModel):
     """A Sign-in with Ethereum (EIP-4361) message."""
 
+    scheme: Optional[str] = None
+    """RFC 3986 URI scheme for the authority that is requesting the signing."""
     domain: str = Field(pattern="^[^/?#]+$")
     """RFC 4501 dns authority that is requesting the signing."""
     address: ChecksumAddress
@@ -234,6 +242,8 @@ def prepare_message(self) -> str:
         :return: EIP-4361 formatted message, ready for EIP-191 signing.
         """
         header = f"{self.domain} wants you to sign in with your Ethereum account:"
+        if self.scheme:
+            header = f"{self.scheme}://{header}"
 
         uri_field = f"URI: {self.uri}"
 
@@ -281,6 +291,7 @@ def verify(
         self,
         signature: str,
         *,
+        scheme: Optional[str] = None,
         domain: Optional[str] = None,
         nonce: Optional[str] = None,
         timestamp: Optional[datetime] = None,
@@ -302,6 +313,8 @@ def verify(
         message = encode_defunct(text=self.prepare_message())
         w3 = Web3(provider=provider)
 
+        if scheme is not None and self.scheme != scheme:
+            raise SchemeMismatch()
         if domain is not None and self.domain != domain:
             raise DomainMismatch()
         if nonce is not None and self.nonce != nonce:
diff --git a/tests/siwe b/tests/siwe
index 903faa9..4290e1f 160000
--- a/tests/siwe
+++ b/tests/siwe
@@ -1 +1 @@
-Subproject commit 903faa93c3125e4e1ac144b76cd5b43ba0fdd3e9
+Subproject commit 4290e1fb3702c97ffee16112492216ad4c4654c1
diff --git a/tests/test_siwe.py b/tests/test_siwe.py
index ba85c95..edb9d08 100644
--- a/tests/test_siwe.py
+++ b/tests/test_siwe.py
@@ -33,7 +33,7 @@ def test_valid_message(self, abnf, test_name, test):
         siwe_message = SiweMessage(message=test["message"], abnf=abnf)
         for key, value in test["fields"].items():
             v = getattr(siwe_message, key)
-            if not isinstance(v, int) and not isinstance(v, list):
+            if not (isinstance(v, int) or isinstance(v, list) or v is None):
                 v = str(v)
             assert v == value