diff --git a/payment.go b/payment.go
index 1ee1fbb..e2b3792 100644
--- a/payment.go
+++ b/payment.go
@@ -18,9 +18,9 @@ var (
 	amexCardFormatString                = "^3[47][0-9]{13}$"
 	visaCardFormatString                = "^4[0-9]{15}$"
 	mastercardCardFormatString          = "^(?:5[1-5][0-9]{2}|222[1-9]|22[3-9][0-9]|2[3-6][0-9]{2}|27[01][0-9]|2720)[0-9]{12}$"
-	discoverCardFormatString            = "^65[0-9]{14}|64[4-9][0-9]{13}|6011[0-9]{12}|(622(?:12[6-9]|1[3-9][0-9]|[2-8][0-9][0-9]|9[01][0-9]|92[0-5])[0-9]{10})$"
-	jcbCardFormatString                 = "^(?:2131|1800|35[0-9]{3})[0-9]{11}$"
-	dinersClubInternationalFormatString = "^3(?:0[0-5]|[68][0-9])[0-9]{11}$"
+	discoverCardFormatString            = "^65[0-9]{14,17}|64[4-9][0-9]{13,16}|6011[0-9]{12,15}|(622(?:12[6-9]|1[3-9][0-9]|[2-8][0-9][0-9]|9[01][0-9]|92[0-5])[0-9]{10,13})$"
+	jcbCardFormatString                 = "^(?:2131|1800|35[0-9]{2})[0-9]{12,15}$"
+	dinersClubInternationalFormatString = "^3(?:0[0-5]|[68][0-9])[0-9]{11,16}$"
 
 	AMEXCardFormatRegex     = regexp.MustCompile(amexCardFormatString)
 	VISACardFormatRegex     = regexp.MustCompile(visaCardFormatString)
diff --git a/payment_test.go b/payment_test.go
index 0dfcba6..f51aa3d 100644
--- a/payment_test.go
+++ b/payment_test.go
@@ -3,79 +3,86 @@ package dough
 import "testing"
 
 var testCards = map[string]string{
-	"4111111111111111": "visa",
-	"4457010000000009": "visa",
-	"4457010100000008": "visa",
-	"4457010140000141": "visa",
-	"4457010200000247": "visa",
-	"4100200300011001": "visa",
-	"4100200300012009": "visa",
-	"4100200300013007": "visa",
-	"4100200310000002": "visa",
-	"4024720001231239": "visa",
-	"4457012400000001": "visa",
-	"4457013200000001": "visa",
-	"4457119922390123": "visa",
-	"4457000300000007": "visa",
-	"4457000100000009": "visa",
-	"4457003100000003": "visa",
-	"4457000400000006": "visa",
-	"4457000200000008": "visa",
-	"4457000800000002": "visa",
-	"4457000900000001": "visa",
-	"4457001000000008": "visa",
-	"4005550000081019": "visa",
-	"4000000000000002": "visa",
-	"2223000148400010": "mastercard",
-	"2223000048400011": "mastercard",
-	"2223280062080010": "mastercard",
-	"2222630061560019": "mastercard",
-	"2222470061880012": "mastercard",
-	"2222400061240016": "mastercard",
-	"2222400041240011": "mastercard",
-	"2223520063560019": "mastercard",
-	"2223520043560014": "mastercard",
-	"2222420040560011": "mastercard",
-	"2222410040360017": "mastercard",
-	"2223020040760014": "mastercard",
-	"5112000100000003": "mastercard",
-	"5112002100000009": "mastercard",
-	"5112002200000008": "mastercard",
-	"5112000200000002": "mastercard",
-	"5112000300000001": "mastercard",
-	"5112000400000000": "mastercard",
-	"5112010400000009": "mastercard",
-	"5112000600000008": "mastercard",
-	"5112010000000003": "mastercard",
-	"5112010100000002": "mastercard",
-	"5112010140000004": "mastercard",
-	"5154605300000121": "mastercard",
-	"5167001020236549": "mastercard",
-	"5500000254444445": "mastercard",
-	"5592106621450897": "mastercard",
-	"5590409551104142": "mastercard",
-	"5587755665222179": "mastercard",
-	"5445840176552850": "mastercard",
-	"5390016478904678": "mastercard",
-	"5112010201000109": "mastercard",
-	"5112010202000108": "mastercard",
-	"5194560012341234": "mastercard",
-	"5435101234510196": "mastercard",
-	"5407102010000018": "mastercard",
-	"5112000900000005": "mastercard",
-	"6011010000000003": "discover",
-	"6011010100000002": "discover",
-	"6011010140000004": "discover",
-	"375000026600004":  "amex",
-	"375001000000005":  "amex",
-	"375001010000003":  "amex",
-	"375001014000009":  "amex",
-	"341234567890127":  "amex",
-	"378734493671000":  "amex",
-	"3530111333300000": "jcb",
-	"3566002020360505": "jcb",
-	"30569309025904":   "diners",
-	"38520000023237":   "diners",
+	"4111111111111111":    "visa",
+	"4457010000000009":    "visa",
+	"4457010100000008":    "visa",
+	"4457010140000141":    "visa",
+	"4457010200000247":    "visa",
+	"4100200300011001":    "visa",
+	"4100200300012009":    "visa",
+	"4100200300013007":    "visa",
+	"4100200310000002":    "visa",
+	"4024720001231239":    "visa",
+	"4457012400000001":    "visa",
+	"4457013200000001":    "visa",
+	"4457119922390123":    "visa",
+	"4457000300000007":    "visa",
+	"4457000100000009":    "visa",
+	"4457003100000003":    "visa",
+	"4457000400000006":    "visa",
+	"4457000200000008":    "visa",
+	"4457000800000002":    "visa",
+	"4457000900000001":    "visa",
+	"4457001000000008":    "visa",
+	"4005550000081019":    "visa",
+	"4000000000000002":    "visa",
+	"2223000148400010":    "mastercard",
+	"2223000048400011":    "mastercard",
+	"2223280062080010":    "mastercard",
+	"2222630061560019":    "mastercard",
+	"2222470061880012":    "mastercard",
+	"2222400061240016":    "mastercard",
+	"2222400041240011":    "mastercard",
+	"2223520063560019":    "mastercard",
+	"2223520043560014":    "mastercard",
+	"2222420040560011":    "mastercard",
+	"2222410040360017":    "mastercard",
+	"2223020040760014":    "mastercard",
+	"5112000100000003":    "mastercard",
+	"5112002100000009":    "mastercard",
+	"5112002200000008":    "mastercard",
+	"5112000200000002":    "mastercard",
+	"5112000300000001":    "mastercard",
+	"5112000400000000":    "mastercard",
+	"5112010400000009":    "mastercard",
+	"5112000600000008":    "mastercard",
+	"5112010000000003":    "mastercard",
+	"5112010100000002":    "mastercard",
+	"5112010140000004":    "mastercard",
+	"5154605300000121":    "mastercard",
+	"5167001020236549":    "mastercard",
+	"5500000254444445":    "mastercard",
+	"5592106621450897":    "mastercard",
+	"5590409551104142":    "mastercard",
+	"5587755665222179":    "mastercard",
+	"5445840176552850":    "mastercard",
+	"5390016478904678":    "mastercard",
+	"5112010201000109":    "mastercard",
+	"5112010202000108":    "mastercard",
+	"5194560012341234":    "mastercard",
+	"5435101234510196":    "mastercard",
+	"5407102010000018":    "mastercard",
+	"5112000900000005":    "mastercard",
+	"6011010000000003":    "discover",
+	"6011010100000002":    "discover",
+	"6011010140000004":    "discover",
+	"6011010000000003011": "discover",
+	"6011010100000002011": "discover",
+	"6011010140000000011": "discover",
+	"375000026600004":     "amex",
+	"375001000000005":     "amex",
+	"375001010000003":     "amex",
+	"375001014000009":     "amex",
+	"341234567890127":     "amex",
+	"378734493671000":     "amex",
+	"3530111333300000":    "jcb",
+	"3566002020360505":    "jcb",
+	"3530111333300000332": "jcb",
+	"3566002020360505005": "jcb",
+	"30569309025904":      "diners",
+	"38520000023237":      "diners",
+	"3056930902590411014": "diners",
+	"3852000002323711017": "diners",
 }
 
 func TestValidLuhn(t *testing.T) {