diff --git a/builder/amazon/common/run_config.go b/builder/amazon/common/run_config.go
index c44c5db05..b3fc15a94 100644
--- a/builder/amazon/common/run_config.go
+++ b/builder/amazon/common/run_config.go
@@ -15,13 +15,13 @@ import (
 var reShutdownBehavior = regexp.MustCompile("^(stop|terminate)$")
 
 type DynamicAmiOptions struct {
-	Filters     map[*string]*string
-	Owners      []*string
-	Most_recent bool
+	Filters    map[*string]*string
+	Owners     []*string
+	MostRecent bool `mapstructure:"most_recent"`
 }
 
-func (d *DynamicAmiOptions) Validate() bool {
-	return true
+func (d *DynamicAmiOptions) Empty() bool {
+	return len(d.Owners) == 0 && len(d.Filters) == 0
 }
 
 // RunConfig contains configuration for running an instance from a source
@@ -67,7 +67,7 @@ func (c *RunConfig) Prepare(ctx *interpolate.Context) []error {
 
 	// Validation
 	errs := c.Comm.Prepare(ctx)
-	if c.SourceAmi == "" {
+	if c.SourceAmi == "" && c.DynamicSourceAmi.Empty() {
 		errs = append(errs, errors.New("A source_ami or dynamic_source_ami must be specified"))
 	}
 
diff --git a/builder/amazon/common/step_source_ami_info.go b/builder/amazon/common/step_source_ami_info.go
index a349f3bd9..6946650c1 100644
--- a/builder/amazon/common/step_source_ami_info.go
+++ b/builder/amazon/common/step_source_ami_info.go
@@ -2,6 +2,9 @@ package common
 
 import (
 	"fmt"
+	"log"
+	"sort"
+	"time"
 
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/mitchellh/multistep"
@@ -23,11 +26,6 @@ type StepSourceAMIInfo struct {
 func buildAmiFilters(input map[*string]*string) []*ec2.Filter {
 	var filters []*ec2.Filter
 	for k, v := range input {
-		/*m := v.(map[string]interface{})
-		  var filterValues []*string
-		  for _, e := range m["values"].([]interface{}) {
-		      filterValues = append(filterValues, aws.String(e.(string)))
-		  }*/
 		filters = append(filters, &ec2.Filter{
 			Name:   k,
 			Values: []*string{v},
@@ -36,17 +34,40 @@ func buildAmiFilters(input map[*string]*string) []*ec2.Filter {
 	return filters
 }
 
+type imageSort []*ec2.Image
+
+func (a imageSort) Len() int      { return len(a) }
+func (a imageSort) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
+func (a imageSort) Less(i, j int) bool {
+	itime, _ := time.Parse(time.RFC3339, *a[i].CreationDate)
+	jtime, _ := time.Parse(time.RFC3339, *a[j].CreationDate)
+	return itime.Unix() < jtime.Unix()
+}
+
+// Returns the most recent AMI out of a slice of images.
+func mostRecentAmi(images []*ec2.Image) *ec2.Image {
+	sortedImages := images
+	sort.Sort(imageSort(sortedImages))
+	return sortedImages[len(sortedImages)-1]
+}
+
 func (s *StepSourceAMIInfo) Run(state multistep.StateBag) multistep.StepAction {
 	ec2conn := state.Get("ec2").(*ec2.EC2)
 	ui := state.Get("ui").(packer.Ui)
 
 	params := &ec2.DescribeImagesInput{}
-	params.Filters = buildAmiFilters(s.AmiFilters.Filters)
-	params.Owners = s.AmiFilters.Owners
-	ui.Say(fmt.Sprintf("Using AMI Filters %v", params))
+
+	if s.SourceAmi != "" {
+		params.ImageIds = []*string{&s.SourceAmi}
+	}
+
+	// We have filters to apply
+	if len(s.AmiFilters.Filters) > 0 {
+		params.Filters = buildAmiFilters(s.AmiFilters.Filters)
+	}
+
+	log.Printf("Using AMI Filters %v", params)
 	imageResp, err := ec2conn.DescribeImages(params)
-	//ui.Say(fmt.Sprintf("Inspecting the source AMI (%s)...", s.SourceAmi))
-	//imageResp, err := ec2conn.DescribeImages(&ec2.DescribeImagesInput{ImageIds: []*string{&s.SourceAmi}})
 	if err != nil {
 		err := fmt.Errorf("Error querying AMI: %s", err)
 		state.Put("error", err)
@@ -55,14 +76,27 @@ func (s *StepSourceAMIInfo) Run(state multistep.StateBag) multistep.StepAction {
 	}
 
 	if len(imageResp.Images) == 0 {
-		err := fmt.Errorf("Source AMI '%s' was not found!", s.SourceAmi)
+		err := fmt.Errorf("No AMI was found matching filters: %v", params)
 		state.Put("error", err)
 		ui.Error(err.Error())
 		return multistep.ActionHalt
 	}
 
-	image := imageResp.Images[0]
-	ui.Say(fmt.Sprintf("Got Image %v", image))
+	if len(imageResp.Images) > 1 && s.AmiFilters.MostRecent == false {
+		err := fmt.Errorf("Your query returned more than one result. Please try a more specific search, or set most_recent to true.")
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
+	}
+
+	var image *ec2.Image
+	if s.AmiFilters.MostRecent {
+		image = mostRecentAmi(imageResp.Images)
+	} else {
+		image = imageResp.Images[0]
+	}
+
+	log.Printf(fmt.Sprintf("Got Image %v", image))
 
 	// Enhanced Networking (SriovNetSupport) can only be enabled on HVM AMIs.
 	// See http://goo.gl/icuXh5