diff --git a/.drone.yml b/.drone.yml
index d715e37..c63a2d8 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -14,6 +14,7 @@ steps:
   - apk --no-cache add build-base
   - go vet -v -buildvcs=false ./checker
   - go vet -v -buildvcs=false ./token-validator
+  - cd ./pkg/token-validator && go test && cd -
   - cd ./pkg/minichecker/cmd && go vet -v -buildvcs=false . && cd -
   - cd ./pkg/arp-spoofer/cmd && go vet -v -buildvcs=false . && go build -buildvcs=false -v -ldflags="-s -w" . && cd -
   - cd ./pkg/login-validator/cmd && go vet -v -buildvcs=false . && go build -buildvcs=false -v -ldflags="-s -w" . && cd -
@@ -46,6 +47,7 @@ steps:
   - apk --no-cache add build-base
   - go vet -v -buildvcs=false ./checker
   - go vet -v -buildvcs=false ./token-validator
+  - cd ./pkg/token-validator && go test && cd -
   - cd ./pkg/minichecker/cmd && go vet -v -buildvcs=false . && cd -
   - cd ./pkg/arp-spoofer/cmd && go vet -v -buildvcs=false . && go build -buildvcs=false -v -ldflags="-s -w" . && cd -
   - cd ./pkg/login-validator/cmd && go vet -v -buildvcs=false . && go build -buildvcs=false -v -ldflags="-s -w" . && cd -
diff --git a/token-validator/ip.go b/token-validator/ip.go
index 9805562..206f526 100644
--- a/token-validator/ip.go
+++ b/token-validator/ip.go
@@ -18,9 +18,10 @@ func init() {
 }
 
 func IPSuffix(s *adlin.Student, network net.IPNet) net.IP {
-	ipshift := s.Id*4 + 10
+	ipshift := s.Id*4 + 7
 
-	myIP := network.IP
+	myIP := make(net.IP, len(network.IP))
+	copy(myIP, network.IP)
 
 	if ipshift > 254 {
 		myIP[len(myIP)-2] += byte(ipshift / 254)
diff --git a/token-validator/ip_test.go b/token-validator/ip_test.go
new file mode 100644
index 0000000..688dc14
--- /dev/null
+++ b/token-validator/ip_test.go
@@ -0,0 +1,53 @@
+package main
+
+import (
+	"log"
+	"net"
+	"testing"
+
+	"git.nemunai.re/srs/adlin/libadlin"
+)
+
+func TestIPSuffix(t *testing.T) {
+	network := net.IPNet{IP: net.ParseIP("172.23.0.0"), Mask: net.CIDRMask(17, 32)}
+
+	std := &adlin.Student{Id: 1}
+	ip := IPSuffix(std, network)
+
+	log.Println(ip)
+
+	if ip.String() != "172.23.0.11" {
+		t.Fatalf(`IPSuffix(%v, %q) = %q, expected %q`, std, network.String(), ip.String(), "172.23.0.11")
+	}
+
+	std = &adlin.Student{Id: 60}
+	ip = IPSuffix(std, network)
+
+	if ip.String() != "172.23.0.247" {
+		t.Fatalf(`IPSuffix(%v, %q) = %q, expected %q`, std, network.String(), ip.String(), "172.23.0.247")
+	}
+
+	std = &adlin.Student{Id: 62}
+	ip = IPSuffix(std, network)
+
+	if ip.String() != "172.23.1.1" {
+		t.Fatalf(`IPSuffix(%v, %q) = %q, expected %q`, std, network.String(), ip.String(), "172.23.1.1")
+	}
+
+	std = &adlin.Student{Id: 70}
+	ip = IPSuffix(std, network)
+
+	if ip.String() != "172.23.1.33" {
+		t.Fatalf(`IPSuffix(%v, %q) = %q, expected %q`, std, network.String(), ip.String(), "172.23.1.33")
+	}
+
+	// Other network
+	network = net.IPNet{IP: net.ParseIP("192.168.42.0"), Mask: net.CIDRMask(17, 32)}
+
+	std = &adlin.Student{Id: 70}
+	ip = IPSuffix(std, network)
+
+	if ip.String() != "192.168.43.33" {
+		t.Fatalf(`IPSuffix(%v, %q) = %q, expected %q`, std, network.String(), ip.String(), "192.168.43.33")
+	}
+}