diff --git a/utils.go b/utils.go
index c1a39bb8..004bf306 100644
--- a/utils.go
+++ b/utils.go
@@ -12,7 +12,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"net"
-	"sort"
 	"strings"
 
 	"github.com/rs/zerolog/log"
@@ -190,7 +189,7 @@ func (h *Headscale) getAvailableIP(ipPrefix netaddr.IPPrefix) (*netaddr.IP, erro
 	}
 }
 
-func (h *Headscale) getUsedIPs() (netaddr.IPSet, error) {
+func (h *Headscale) getUsedIPs() (*netaddr.IPSet, error) {
 	// FIXME: This really deserves a better data model,
 	// but this was quick to get running and it should be enough
 	// to begin experimenting with a dual stack tailnet.
@@ -206,7 +205,7 @@ func (h *Headscale) getUsedIPs() (netaddr.IPSet, error) {
 		var machineAddresses MachineAddresses
 		err := machineAddresses.Scan(slice)
 		if err != nil {
-			return netaddr.IPSet{}, fmt.Errorf(
+			return &netaddr.IPSet{}, fmt.Errorf(
 				"failed to read ip from database: %w",
 				err,
 			)
@@ -221,7 +220,15 @@ func (h *Headscale) getUsedIPs() (netaddr.IPSet, error) {
 		Interface("addresses", ips).
 		Msg("Parsed ip addresses that has been allocated from databases")
 
-	return netaddr.IPSet{}, nil
+	ipSet, err := ips.IPSet()
+	if err != nil {
+		return &netaddr.IPSet{}, fmt.Errorf(
+			"failed to build IP Set: %w",
+			err,
+		)
+	}
+
+	return ipSet, nil
 }
 
 func containsString(ss []string, s string) bool {
diff --git a/utils_test.go b/utils_test.go
index feb44d5a..896040c8 100644
--- a/utils_test.go
+++ b/utils_test.go
@@ -48,9 +48,12 @@ func (s *Suite) TestGetUsedIps(c *check.C) {
 	c.Assert(err, check.IsNil)
 
 	expected := netaddr.MustParseIP("10.27.0.1")
+	expectedIPSetBuilder := netaddr.IPSetBuilder{}
+	expectedIPSetBuilder.Add(expected)
+	expectedIPSet, _ := expectedIPSetBuilder.IPSet()
 
-	c.Assert(len(usedIps), check.Equals, 1)
-	c.Assert(usedIps[0], check.Equals, expected)
+	c.Assert(usedIps.Equal(expectedIPSet), check.Equals, true)
+	c.Assert(usedIps.Contains(expected), check.Equals, true)
 
 	machine1, err := app.GetMachineByID(0)
 	c.Assert(err, check.IsNil)
@@ -64,6 +67,8 @@ func (s *Suite) TestGetMultiIp(c *check.C) {
 	c.Assert(err, check.IsNil)
 
 	for index := 1; index <= 350; index++ {
+		app.ipAllocationMutex.Lock()
+
 		ips, err := app.getAvailableIPs()
 		c.Assert(err, check.IsNil)
 
@@ -86,17 +91,30 @@ func (s *Suite) TestGetMultiIp(c *check.C) {
 			IPAddresses:    ips,
 		}
 		app.db.Save(&machine)
+
+		app.ipAllocationMutex.Unlock()
 	}
 
 	usedIps, err := app.getUsedIPs()
-
 	c.Assert(err, check.IsNil)
 
-	c.Assert(len(usedIps), check.Equals, 350)
+	expected0 := netaddr.MustParseIP("10.27.0.1")
+	expected9 := netaddr.MustParseIP("10.27.0.10")
+	expected300 := netaddr.MustParseIP("10.27.0.45")
 
-	c.Assert(usedIps[0], check.Equals, netaddr.MustParseIP("10.27.0.1"))
-	c.Assert(usedIps[9], check.Equals, netaddr.MustParseIP("10.27.0.10"))
-	c.Assert(usedIps[300], check.Equals, netaddr.MustParseIP("10.27.1.45"))
+	notExpectedIPSetBuilder := netaddr.IPSetBuilder{}
+	notExpectedIPSetBuilder.Add(expected0)
+	notExpectedIPSetBuilder.Add(expected9)
+	notExpectedIPSetBuilder.Add(expected300)
+	notExpectedIPSet, err := notExpectedIPSetBuilder.IPSet()
+	c.Assert(err, check.IsNil)
+
+	// We actually expect it to be a lot larger
+	c.Assert(usedIps.Equal(notExpectedIPSet), check.Equals, false)
+
+	c.Assert(usedIps.Contains(expected0), check.Equals, true)
+	c.Assert(usedIps.Contains(expected9), check.Equals, true)
+	c.Assert(usedIps.Contains(expected300), check.Equals, true)
 
 	// Check that we can read back the IPs
 	machine1, err := app.GetMachineByID(1)