Index: CryptoPassphrase.m
==================================================================
--- CryptoPassphrase.m
+++ CryptoPassphrase.m
@@ -120,11 +120,17 @@
 
 	if (lengthString != nil) {
 		bool invalid = false;
 
 		@try {
-			generator.length = (size_t)lengthString.decimalValue;
+			unsigned long long length =
+			    lengthString.unsignedLongLongValue;
+
+			if (length > SIZE_MAX)
+				@throw [OFOutOfRangeException exception];
+
+			generator.length = (size_t)length;
 		} @catch (OFInvalidFormatException *e) {
 			invalid = true;
 		} @catch (OFOutOfRangeException *e) {
 			invalid = true;
 		}