diff --git a/lib/common/common.go b/lib/common/common.go
index 5fd1d460..5275d5a4 100644
--- a/lib/common/common.go
+++ b/lib/common/common.go
@@ -16,6 +16,9 @@
 package common
 
 import (
+	"fmt"
+	"regexp"
+
 	"github.com/appc/docker2aci/lib/internal/docker"
 	"github.com/appc/docker2aci/lib/internal/types"
 )
@@ -27,6 +30,10 @@ const (
 	GzipCompression
 )
 
+var (
+	validId = regexp.MustCompile(`^(\w+:)?([A-Fa-f0-9]+)$`)
+)
+
 type ParsedDockerURL types.ParsedDockerURL
 
 const (
@@ -60,3 +67,11 @@ func ParseDockerURL(arg string) (*ParsedDockerURL, error) {
 	p, err := docker.ParseDockerURL(arg)
 	return (*ParsedDockerURL)(p), err
 }
+
+// ValidateLayerId validates a layer ID
+func ValidateLayerId(id string) error {
+	if ok := validId.MatchString(id); !ok {
+		return fmt.Errorf("invalid layer ID %q", id)
+	}
+	return nil
+}
diff --git a/lib/internal/backend/file/file.go b/lib/internal/backend/file/file.go
index a83402df..708e333a 100644
--- a/lib/internal/backend/file/file.go
+++ b/lib/internal/backend/file/file.go
@@ -73,6 +73,9 @@ func (lb *FileBackend) BuildACI(layerIDs []string, dockerURL *types.ParsedDocker
 	var aciManifests []*schema.ImageManifest
 	var curPwl []string
 	for i := len(layerIDs) - 1; i >= 0; i-- {
+		if err := common.ValidateLayerId(layerIDs[i]); err != nil {
+			return nil, nil, err
+		}
 		tmpDir, err := ioutil.TempDir(tmpBaseDir, "docker2aci-")
 		if err != nil {
 			return nil, nil, fmt.Errorf("error creating dir: %v", err)
@@ -279,14 +282,24 @@ func extractEmbeddedLayer(file *os.File, layerID string, outputPath string) (*os
 	return layerFile, nil
 }
 
+// getAncestry computes an image ancestry, returning an ordered list
+// of dependencies starting from the topmost image to the base.
+// It checks for dependency loops via duplicate detection in the image
+// chain and errors out in such cases.
 func getAncestry(file *os.File, imgID string) ([]string, error) {
 	var ancestry []string
+	deps := make(map[string]bool)
 
 	curImgID := imgID
 
 	var err error
 	for curImgID != "" {
+		if deps[curImgID] {
+			return nil, fmt.Errorf("dependency loop detected at image %q", curImgID)
+		}
+		deps[curImgID] = true
 		ancestry = append(ancestry, curImgID)
+		log.Debug(fmt.Sprintf("Getting ancestry for layer %q", curImgID))
 		curImgID, err = getParent(file, curImgID)
 		if err != nil {
 			return nil, err
@@ -328,5 +341,6 @@ func getParent(file *os.File, imgID string) (string, error) {
 		return "", err
 	}
 
+	log.Debug(fmt.Sprintf("Layer %q depends on layer %q", imgID, parent))
 	return parent, nil
 }
diff --git a/lib/internal/backend/repository/repository1.go b/lib/internal/backend/repository/repository1.go
index bc54e47c..7d4fe917 100644
--- a/lib/internal/backend/repository/repository1.go
+++ b/lib/internal/backend/repository/repository1.go
@@ -75,6 +75,9 @@ func (rb *RepositoryBackend) buildACIV1(layerIDs []string, dockerURL *types.Pars
 
 	var doneChannels []chan error
 	for i, layerID := range layerIDs {
+		if err := common.ValidateLayerId(layerID); err != nil {
+			return nil, nil, err
+		}
 		doneChan := make(chan error)
 		doneChannels = append(doneChannels, doneChan)
 		// https://github.com/golang/go/wiki/CommonMistakes
diff --git a/lib/internal/backend/repository/repository2.go b/lib/internal/backend/repository/repository2.go
index d074e9a0..208c9540 100644
--- a/lib/internal/backend/repository/repository2.go
+++ b/lib/internal/backend/repository/repository2.go
@@ -23,7 +23,6 @@ import (
 	"net/http"
 	"os"
 	"path"
-	"regexp"
 	"strconv"
 	"strings"
 	"sync"
@@ -43,8 +42,6 @@ const (
 	defaultIndexURL = "registry-1.docker.io"
 )
 
-var validHex = regexp.MustCompile(`^([a-f0-9]{64})$`)
-
 // A manifest conforming to the docker v2.1 spec
 type v2Manifest struct {
 	Name     string `json:"name"`
@@ -91,6 +88,9 @@ func (rb *RepositoryBackend) buildACIV21(layerIDs []string, dockerURL *types.Par
 	closers := make([]io.ReadCloser, len(layerIDs))
 	var wg sync.WaitGroup
 	for i, layerID := range layerIDs {
+		if err := common.ValidateLayerId(layerID); err != nil {
+			return nil, nil, err
+		}
 		wg.Add(1)
 		errChan := make(chan error, 1)
 		errChannels = append(errChannels, errChan)
@@ -195,6 +195,9 @@ func (rb *RepositoryBackend) buildACIV22(layerIDs []string, dockerURL *types.Par
 
 	resultChan := make(chan layer, len(layerIDs))
 	for i, layerID := range layerIDs {
+		if err := common.ValidateLayerId(layerID); err != nil {
+			return nil, nil, err
+		}
 		// https://github.com/golang/go/wiki/CommonMistakes
 		i := i // golang--
 		layerID := layerID
@@ -436,7 +439,7 @@ func fixManifestLayers(manifest *v2Manifest) error {
 		}
 
 		imgs[i] = img
-		if err := validateV1ID(img.ID); err != nil {
+		if err := common.ValidateLayerId(img.ID); err != nil {
 			return err
 		}
 	}
@@ -471,13 +474,6 @@ func fixManifestLayers(manifest *v2Manifest) error {
 	return nil
 }
 
-func validateV1ID(id string) error {
-	if ok := validHex.MatchString(id); !ok {
-		return fmt.Errorf("image ID %q is invalid", id)
-	}
-	return nil
-}
-
 func (rb *RepositoryBackend) getLayerV2(layerID string, dockerURL *types.ParsedDockerURL, tmpDir string, copier *progressutil.CopyProgressPrinter) (*os.File, io.ReadCloser, error) {
 	var (
 		err error
diff --git a/tests/fixture-test-depsloop/check.sh b/tests/fixture-test-depsloop/check.sh
new file mode 100755
index 00000000..798f4570
--- /dev/null
+++ b/tests/fixture-test-depsloop/check.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+DOCKER2ACI=../bin/docker2aci
+TESTDIR=$1
+TESTNAME=$2
+
+timeout 10s ${DOCKER2ACI} "${TESTDIR}/${TESTNAME}/${TESTNAME}.docker"
+if [ $? -eq 1 ]; then
+	echo "### Test case ${TESTNAME}: SUCCESS"
+	exit 0
+else
+	echo "### Test case ${TESTNAME}: FAIL"
+	exit 1
+fi
+
diff --git a/tests/fixture-test-depsloop/fixture-test-depsloop.docker b/tests/fixture-test-depsloop/fixture-test-depsloop.docker
new file mode 100644
index 00000000..f5fe5513
Binary files /dev/null and b/tests/fixture-test-depsloop/fixture-test-depsloop.docker differ
diff --git a/tests/fixture-test-invalidlayerid/check.sh b/tests/fixture-test-invalidlayerid/check.sh
new file mode 100755
index 00000000..bbf0cb4f
--- /dev/null
+++ b/tests/fixture-test-invalidlayerid/check.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+DOCKER2ACI=../bin/docker2aci
+TESTDIR=$1
+TESTNAME=$2
+
+sudo ${DOCKER2ACI} "${TESTDIR}/${TESTNAME}/${TESTNAME}.docker"
+if [ $? -eq 1 ]; then
+	echo "### Test case ${TESTNAME}: SUCCESS"
+	exit 0
+else
+	echo "### Test case ${TESTNAME}: FAIL"
+	exit 1
+fi
+
diff --git a/tests/fixture-test-invalidlayerid/fixture-test-invalidlayerid.docker b/tests/fixture-test-invalidlayerid/fixture-test-invalidlayerid.docker
new file mode 100644
index 00000000..ef246448
Binary files /dev/null and b/tests/fixture-test-invalidlayerid/fixture-test-invalidlayerid.docker differ
diff --git a/tests/test.sh b/tests/test.sh
index 5844c9b0..658b7150 100755
--- a/tests/test.sh
+++ b/tests/test.sh
@@ -45,6 +45,12 @@ RKT=$(which rkt)
 
 DOCKER_STORAGE_BACKEND=$(sudo docker info|grep '^Storage Driver:'|sed 's/Storage Driver: //')
 
+for i in $(find . -maxdepth 1 -type d -name 'fixture-test*') ; do
+	  TESTNAME=$(basename $i)
+	  echo "### Test case ${TESTNAME}..."
+	  $TESTDIR/${TESTNAME}/check.sh "${TESTDIR}" "${TESTNAME}"
+done
+
 for i in $(find . -maxdepth 1 -type d -name 'test-*') ; do
 	TESTNAME=$(basename $i)
 	echo "### Test case ${TESTNAME}: build..."
@@ -81,4 +87,3 @@ for i in $(find . -maxdepth 1 -type d -name 'test-*') ; do
 
 	sudo docker rmi $PREFIX/${TESTNAME}
 done
-