diff --git a/.travis.yml b/.travis.yml
index 7c2de7e71..abe45bfa3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,9 +17,7 @@ install: true
 
 script:
   - env | grep TRAVIS_
-  - make .govet
-  - make .golint
   - echo "${TRAVIS_COMMIT_RANGE} -> ${TRAVIS_COMMIT_RANGE/.../..} (travis-ci/travis-ci#4596)"
-  - TRAVIS_COMMIT_RANGE="${TRAVIS_COMMIT_RANGE/.../..}" make .gitvalidation
+  - TRAVIS_COMMIT_RANGE="${TRAVIS_COMMIT_RANGE/.../..}" make test
   - make docs
   - make -C schema test
diff --git a/Makefile b/Makefile
index 770834b7c..d50fc9e3e 100644
--- a/Makefile
+++ b/Makefile
@@ -55,7 +55,14 @@ HOST_GOLANG_VERSION	= $(shell go version | cut -d ' ' -f3 | cut -c 3-)
 # this variable is used like a function. First arg is the minimum version, Second arg is the version to be checked.
 ALLOWED_GO_VERSION	= $(shell test '$(shell /bin/echo -e "$(1)\n$(2)" | sort -V | head -n1)' = '$(1)' && echo 'true')
 
-test: .govet .golint .gitvalidation
+TESTS := .govet .golint .gitvalidation
+
+# (*testing.T).Run is new in 1.7, https://golang.org/doc/go1.7#testing
+ifeq ($(call ALLOWED_GO_VERSION,1.7,$(HOST_GOLANG_VERSION)),true)
+	TESTS += .specs-go
+endif
+
+test: $(TESTS)
 
 .govet:
 	go vet -x ./...
@@ -77,7 +84,10 @@ else
 	git-validation -v -run DCO,short-subject,dangling-whitespace -range $(EPOCH_TEST_COMMIT)..HEAD
 endif
 
-install.tools: .install.golint .install.gitvalidation
+.specs-go:
+	go test ./specs-go
+
+install.tools: .install.golint .install.gitvalidation .install.canonicaljson
 
 # golint does not even build for <go1.6
 .install.golint:
@@ -88,6 +98,9 @@ endif
 .install.gitvalidation:
 	go get -u github.com/vbatts/git-validation
 
+.install.canonicaljson:
+	go get -d -u github.com/docker/go/canonical/json
+
 clean:
 	rm -rf $(OUTPUT_DIRNAME) *~
 	rm -f version.md
diff --git a/specs-go/config.go b/specs-go/config.go
index f2016b04b..82964628b 100644
--- a/specs-go/config.go
+++ b/specs-go/config.go
@@ -84,9 +84,9 @@ type Box struct {
 // User specifies specific user (and group) information for the container process.
 type User struct {
 	// UID is the user id.
-	UID uint32 `json:"uid" platform:"linux,solaris"`
+	UID *uint32 `json:"uid,omitempty" platform:"linux,solaris"`
 	// GID is the group id.
-	GID uint32 `json:"gid" platform:"linux,solaris"`
+	GID *uint32 `json:"gid,omitempty" platform:"linux,solaris"`
 	// AdditionalGids are additional group ids set for the container's process.
 	AdditionalGids []uint32 `json:"additionalGids,omitempty" platform:"linux,solaris"`
 	// Username is the user name.
diff --git a/specs-go/round_trip_test.go b/specs-go/round_trip_test.go
new file mode 100644
index 000000000..f60757573
--- /dev/null
+++ b/specs-go/round_trip_test.go
@@ -0,0 +1,39 @@
+package specs_test
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+
+	"github.com/docker/go/canonical/json"
+	"github.com/opencontainers/runtime-spec/specs-go"
+)
+
+func TestConfigRoundTrip(t *testing.T) {
+	for i, configString := range []string{
+		// canonical version of the config.md example
+		`{"ociVersion":"0.5.0-dev","platform":{"os":"linux","arch":"amd64"},"process":{"terminal":true,"consoleSize":{"height":0,"width":0},"user":{"uid":1,"gid":1,"additionalGids":[5,6]},"args":["sh"],"env":["PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin","TERM=xterm"],"cwd":"/","capabilities":{"bounding":["CAP_AUDIT_WRITE","CAP_KILL","CAP_NET_BIND_SERVICE"],"effective":["CAP_AUDIT_WRITE","CAP_KILL"],"inheritable":["CAP_AUDIT_WRITE","CAP_KILL","CAP_NET_BIND_SERVICE"],"permitted":["CAP_AUDIT_WRITE","CAP_KILL","CAP_NET_BIND_SERVICE"],"ambient":["CAP_NET_BIND_SERVICE"]},"rlimits":[{"type":"RLIMIT_CORE","hard":1024,"soft":1024},{"type":"RLIMIT_NOFILE","hard":1024,"soft":1024}],"noNewPrivileges":true,"apparmorProfile":"acme_secure_profile","selinuxLabel":"system_u:system_r:svirt_lxc_net_t:s0:c124,c675"},"root":{"path":"rootfs","readonly":true},"hostname":"slartibartfast","mounts":[{"destination":"/proc","type":"proc","source":"proc"},{"destination":"/dev","type":"tmpfs","source":"tmpfs","options":["nosuid","strictatime","mode=755","size=65536k"]},{"destination":"/dev/pts","type":"devpts","source":"devpts","options":["nosuid","noexec","newinstance","ptmxmode=0666","mode=0620","gid=5"]},{"destination":"/dev/shm","type":"tmpfs","source":"shm","options":["nosuid","noexec","nodev","mode=1777","size=65536k"]},{"destination":"/dev/mqueue","type":"mqueue","source":"mqueue","options":["nosuid","noexec","nodev"]},{"destination":"/sys","type":"sysfs","source":"sysfs","options":["nosuid","noexec","nodev"]},{"destination":"/sys/fs/cgroup","type":"cgroup","source":"cgroup","options":["nosuid","noexec","nodev","relatime","ro"]}],"hooks":{"prestart":[{"path":"/usr/bin/fix-mounts","args":["fix-mounts","arg1","arg2"],"env":["key1=value1"]},{"path":"/usr/bin/setup-network"}],"poststart":[{"path":"/usr/bin/notify-start","timeout":5}],"poststop":[{"path":"/usr/sbin/cleanup.sh","args":["cleanup.sh","-f"]}]},"annotations":{"com.example.key1":"value1","com.example.key2":"value2"},"linux":{"uidMappings":[{"hostID":1000,"containerID":0,"size":32000}],"gidMappings":[{"hostID":1000,"containerID":0,"size":32000}],"sysctl":{"net.core.somaxconn":"256","net.ipv4.ip_forward":"1"},"resources":{"devices":[{"allow":false,"access":"rwm"},{"allow":true,"type":"c","major":10,"minor":229,"access":"rw"},{"allow":true,"type":"b","major":8,"minor":0,"access":"r"}],"disableOOMKiller":false,"oomScoreAdj":100,"memory":{"limit":536870912,"reservation":536870912,"swap":536870912,"kernel":0,"kernelTCP":0,"swappiness":0},"cpu":{"shares":1024,"quota":1000000,"period":500000,"realtimeRuntime":950000,"realtimePeriod":1000000,"cpus":"2-3","mems":"0-7"},"pids":{"limit":32771},"blockIO":{"blkioWeight":10,"blkioLeafWeight":10,"blkioWeightDevice":[{"major":8,"minor":0,"weight":500,"leafWeight":300},{"major":8,"minor":16,"weight":500}],"blkioThrottleReadBpsDevice":[{"major":8,"minor":0,"rate":600}],"blkioThrottleWriteIOPSDevice":[{"major":8,"minor":16,"rate":300}]},"hugepageLimits":[{"pageSize":"2MB","limit":9223372036854772000}],"network":{"classID":1048577,"priorities":[{"name":"eth0","priority":500},{"name":"eth1","priority":1000}]}},"cgroupsPath":"/myRuntime/myContainer","namespaces":[{"type":"pid"},{"type":"network"},{"type":"ipc"},{"type":"uts"},{"type":"mount"},{"type":"user"},{"type":"cgroup"}],"devices":[{"path":"/dev/fuse","type":"c","major":10,"minor":229,"fileMode":438,"uid":0,"gid":0},{"path":"/dev/sda","type":"b","major":8,"minor":0,"fileMode":432,"uid":0,"gid":0}],"seccomp":{"defaultAction":"SCMP_ACT_ALLOW","architectures":["SCMP_ARCH_X86","SCMP_ARCH_X32"],"syscalls":[{"names":["getcwd","chmod"],"action":"SCMP_ACT_ERRNO","args":null}]},"rootfsPropagation":"slave","maskedPaths":["/proc/kcore","/proc/latency_stats","/proc/timer_stats","/proc/sched_debug"],"readonlyPaths":["/proc/asound","/proc/bus","/proc/fs","/proc/irq","/proc/sys","/proc/sysrq-trigger"],"mountLabel":"system_u:object_r:svirt_sandbox_file_t:s0:c715,c811"}}`,
+
+		// minimal Linux example (removing optional fields from the config.md example)
+		`{"ociVersion":"1.0.0","platform":{"os":"linux","arch":"amd64"},"process":{"user":{"uid":1,"gid":1},"args":["sh"],"cwd":"/"},"root":{"path":"rootfs"}}`,
+
+		// minimal Windows example
+		`{"ociVersion":"1.0.0","platform":{"os":"windows","arch":"amd64"},"process":{"user":{"username":"containeradministrator"},"args":["sh"],"cwd":"C:\\"},"root":{"path":"rootfs"}}`,
+	} {
+		t.Run(fmt.Sprintf("config %d", i), func(t *testing.T) {
+			configBytes := []byte(configString)
+			var configStruct specs.Spec
+			err := json.NewDecoder(bytes.NewReader(configBytes)).Decode(&configStruct)
+			if err != nil {
+				t.Fatalf("failed to decode: %v", err)
+			}
+			outBytes, err := json.Marshal(configStruct)
+			if err != nil {
+				t.Fatalf("failed to encode: %v", err)
+			}
+			if bytes.Compare(configBytes, outBytes) != 0 {
+				t.Fatalf("failed to round-trip:\n%s", string(outBytes))
+			}
+		})
+	}
+}