diff --git a/proxy/common.go b/proxy/common.go
index ddfa85e6..1198ef1b 100644
--- a/proxy/common.go
+++ b/proxy/common.go
@@ -31,8 +31,7 @@ func callWeave(args ...string) ([]byte, error) {
 func weaveCIDRsFromConfig(config *docker.Config) ([]string, bool) {
 	for _, e := range config.Env {
 		if strings.HasPrefix(e, "WEAVE_CIDR=") {
-			result := strings.Trim(e[11:], " ")
-			return strings.Split(strings.TrimSpace(result), " "), result != ""
+			return strings.Fields(e[11:]), true
 		}
 	}
 	return nil, false
diff --git a/proxy/start_container_interceptor.go b/proxy/start_container_interceptor.go
index d35c3afd..8c159d34 100644
--- a/proxy/start_container_interceptor.go
+++ b/proxy/start_container_interceptor.go
@@ -28,6 +28,14 @@ func (i *startContainerInterceptor) InterceptResponse(r *http.Response) error {
 		Debug.Print("No Weave CIDR, ignoring")
 		return nil
 	}
+	if len(cidrs) == 0 {
+		ipamCIDR, err := callWeave("ipam-cidr", container.ID)
+		if err != nil {
+			Warning.Printf("Determining container %s IP via IPAM failed: %v, %v", container.ID, err, string(ipamCIDR))
+			return nil
+		}
+		cidrs = strings.Fields(string(ipamCIDR))
+	}
 	Info.Printf("Attaching container %s with WEAVE_CIDR \"%s\" to weave network", container.ID, strings.Join(cidrs, " "))
 	args := []string{"attach"}
 	args = append(args, cidrs...)
diff --git a/test/660_proxy_ipam_test.sh b/test/660_proxy_ipam_test.sh
new file mode 100755
index 00000000..622307b0
--- /dev/null
+++ b/test/660_proxy_ipam_test.sh
@@ -0,0 +1,19 @@
+#! /bin/bash
+
+. ./config.sh
+
+UNIVERSE=10.2.2.0/24
+
+start_suite "Ping proxied containers over cross-host weave network (with IPAM)"
+
+weave_on $HOST1 launch -iprange $UNIVERSE
+weave_on $HOST1 launch-proxy
+weave_on $HOST2 launch -iprange $UNIVERSE $HOST1
+weave_on $HOST2 launch-proxy
+
+proxy_start_container $HOST1 -e WEAVE_CIDR= --name=c1
+proxy_start_container $HOST2 -e WEAVE_CIDR= --name=c2
+C2=$(container_ip $HOST2 c2)
+assert_raises "exec_on $HOST1 c1 $PING $C2"
+
+end_suite
diff --git a/test/config.sh b/test/config.sh
index b8c657a1..c48844a8 100644
--- a/test/config.sh
+++ b/test/config.sh
@@ -112,6 +112,12 @@ start_container() {
     weave_on $host run "$@" -t gliderlabs/alpine /bin/sh
 }
 
+proxy_start_container() {
+    host=$1
+    shift 1
+    docker -H tcp://$host:12375 run "$@" -dt gliderlabs/alpine /bin/sh
+}
+
 start_container_with_dns() {
     host=$1
     shift 1
diff --git a/weave b/weave
index 45295f52..fef6bd45 100755
--- a/weave
+++ b/weave
@@ -928,6 +928,9 @@ case "$COMMAND" in
         docker_bridge_ip
         echo -n $DOCKER_BRIDGE_IP
         ;;
+    ipam-cidr)
+        get_ipam_cidr "$@" && echo "$CIDR_ARGS"
+        ;;
     start)
         collect_cidr_args "$@"
         shift $CIDR_COUNT