diff --git a/nomad/structs/network.go b/nomad/structs/network.go
index 39292e831..216e51015 100644
--- a/nomad/structs/network.go
+++ b/nomad/structs/network.go
@@ -1,6 +1,7 @@
 package structs
 
 import (
+	"fmt"
 	"math/rand"
 	"net"
 )
@@ -134,7 +135,7 @@ func (idx *NetworkIndex) yieldIP(cb func(net *NetworkResource, ip net.IP) bool)
 
 // AssignNetwork is used to assign network resources given an ask.
 // If the ask cannot be satisfied, returns nil
-func (idx *NetworkIndex) AssignNetwork(ask *NetworkResource) (out *NetworkResource) {
+func (idx *NetworkIndex) AssignNetwork(ask *NetworkResource) (out *NetworkResource, err error) {
 	idx.yieldIP(func(n *NetworkResource, ip net.IP) (stop bool) {
 		// Convert the IP to a string
 		ipStr := ip.String()
@@ -143,13 +144,15 @@ func (idx *NetworkIndex) AssignNetwork(ask *NetworkResource) (out *NetworkResour
 		availBandwidth := idx.AvailBandwidth[n.Device]
 		usedBandwidth := idx.UsedBandwidth[n.Device]
 		if usedBandwidth+ask.MBits > availBandwidth {
+			err = fmt.Errorf("bandwidth exceeded")
 			return
 		}
 
 		// Check if any of the reserved ports are in use
 		for _, port := range ask.ReservedPorts {
 			if _, ok := idx.UsedPorts[ipStr][port]; ok {
-				return false
+				err = fmt.Errorf("reserved port collision")
+				return
 			}
 		}
 
@@ -166,6 +169,7 @@ func (idx *NetworkIndex) AssignNetwork(ask *NetworkResource) (out *NetworkResour
 		PICK:
 			attempts++
 			if attempts > maxRandPortAttempts {
+				err = fmt.Errorf("dynamic port selection failed")
 				return
 			}
 
@@ -181,6 +185,7 @@ func (idx *NetworkIndex) AssignNetwork(ask *NetworkResource) (out *NetworkResour
 
 		// Stop, we have an offer!
 		out = offer
+		err = nil
 		return true
 	})
 	return
diff --git a/nomad/structs/network_test.go b/nomad/structs/network_test.go
index 802964472..1db783d65 100644
--- a/nomad/structs/network_test.go
+++ b/nomad/structs/network_test.go
@@ -271,7 +271,10 @@ func TestNetworkIndex_AssignNetwork(t *testing.T) {
 	ask := &NetworkResource{
 		ReservedPorts: []int{8000},
 	}
-	offer := idx.AssignNetwork(ask)
+	offer, err := idx.AssignNetwork(ask)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
 	if offer == nil {
 		t.Fatalf("bad")
 	}
@@ -286,7 +289,10 @@ func TestNetworkIndex_AssignNetwork(t *testing.T) {
 	ask = &NetworkResource{
 		DynamicPorts: 3,
 	}
-	offer = idx.AssignNetwork(ask)
+	offer, err = idx.AssignNetwork(ask)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
 	if offer == nil {
 		t.Fatalf("bad")
 	}
@@ -302,7 +308,10 @@ func TestNetworkIndex_AssignNetwork(t *testing.T) {
 		ReservedPorts: []int{12345},
 		DynamicPorts:  3,
 	}
-	offer = idx.AssignNetwork(ask)
+	offer, err = idx.AssignNetwork(ask)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
 	if offer == nil {
 		t.Fatalf("bad")
 	}
@@ -317,7 +326,10 @@ func TestNetworkIndex_AssignNetwork(t *testing.T) {
 	ask = &NetworkResource{
 		MBits: 1000,
 	}
-	offer = idx.AssignNetwork(ask)
+	offer, err = idx.AssignNetwork(ask)
+	if err.Error() != "bandwidth exceeded" {
+		t.Fatalf("err: %v", err)
+	}
 	if offer != nil {
 		t.Fatalf("bad")
 	}
diff --git a/nomad/structs/structs.go b/nomad/structs/structs.go
index f5479c3bc..23633a1af 100644
--- a/nomad/structs/structs.go
+++ b/nomad/structs/structs.go
@@ -594,7 +594,7 @@ func (r *Resources) Add(delta *Resources) error {
 		// Find the matching interface by IP or CIDR
 		idx := r.NetIndex(n)
 		if idx == -1 {
-			r.Networks = append(r.Networks, n)
+			r.Networks = append(r.Networks, n.Copy())
 		} else {
 			r.Networks[idx].Add(n)
 		}