diff --git a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
index 59aaf1933db..0787f90eb1e 100644
--- a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
+++ b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
@@ -308,3 +308,10 @@ bool SignedBigInteger::operator>=(const SignedBigInteger& other) const
 }
 
 }
+
+ErrorOr<void> AK::Formatter<Crypto::SignedBigInteger>::format(FormatBuilder& fmtbuilder, const Crypto::SignedBigInteger& value)
+{
+    if (value.is_negative())
+        TRY(fmtbuilder.put_string("-"));
+    return Formatter<Crypto::UnsignedBigInteger>::format(fmtbuilder, value.unsigned_value());
+}
diff --git a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h
index f85a4969d96..9bec7187944 100644
--- a/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h
+++ b/Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h
@@ -143,6 +143,11 @@ struct SignedDivisionResult {
 
 }
 
+template<>
+struct AK::Formatter<Crypto::SignedBigInteger> : AK::Formatter<Crypto::UnsignedBigInteger> {
+    ErrorOr<void> format(FormatBuilder&, Crypto::SignedBigInteger const&);
+};
+
 inline Crypto::SignedBigInteger
 operator""_sbigint(const char* string, size_t length)
 {