diff --git a/hcl2template/parser.go b/hcl2template/parser.go
index 5e2670bb5..1bc5d6467 100644
--- a/hcl2template/parser.go
+++ b/hcl2template/parser.go
@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"reflect"
 
+	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/go-version"
 	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/hcl/v2/ext/dynblock"
@@ -403,6 +404,8 @@ func (cfg *PackerConfig) buildPrereqsDAG() (*dag.AcyclicGraph, error) {
 
 	verticesMap := map[string]dag.Vertex{}
 
+	var err error
+
 	// Do a first pass to create all the vertices
 	for ref := range cfg.Datasources {
 		// We keep a reference to the datasource separately from where it
@@ -434,27 +437,48 @@ func (cfg *PackerConfig) buildPrereqsDAG() (*dag.AcyclicGraph, error) {
 	for _, ds := range cfg.Datasources {
 		dsName := fmt.Sprintf("data.%s", ds.Name())
 
+		source := verticesMap[dsName]
+		if source == nil {
+			err = multierror.Append(err, fmt.Errorf("unable to find source vertex %q for dependency analysis, this is likely a Packer bug", dsName))
+			continue
+		}
+
 		for _, dep := range ds.Dependencies {
-			retGraph.Connect(
-				dag.BasicEdge(verticesMap[dsName],
-					verticesMap[dep.String()]))
+			target := verticesMap[dep.String()]
+			if target == nil {
+				err = multierror.Append(err, fmt.Errorf("could not get dependency %q for %q, %q missing in template", dep.String(), dsName, dep.String()))
+				continue
+			}
+
+			retGraph.Connect(dag.BasicEdge(source, target))
 		}
 	}
 	for _, loc := range cfg.LocalBlocks {
 		locName := fmt.Sprintf("local.%s", loc.LocalName)
 
+		source := verticesMap[locName]
+		if source == nil {
+			err = multierror.Append(err, fmt.Errorf("unable to find source vertex %q for dependency analysis, this is likely a Packer bug", locName))
+			continue
+		}
+
 		for _, dep := range loc.dependencies {
-			retGraph.Connect(
-				dag.BasicEdge(verticesMap[locName],
-					verticesMap[dep.String()]))
+			target := verticesMap[dep.String()]
+
+			if target == nil {
+				err = multierror.Append(err, fmt.Errorf("could not get dependency %q for %q, %q missing in template", dep.String(), locName, dep.String()))
+				continue
+			}
+
+			retGraph.Connect(dag.BasicEdge(source, target))
 		}
 	}
 
-	if err := retGraph.Validate(); err != nil {
-		return nil, err
+	if validateErr := retGraph.Validate(); validateErr != nil {
+		err = multierror.Append(err, validateErr)
 	}
 
-	return &retGraph, nil
+	return &retGraph, err
 }
 
 func (cfg *PackerConfig) evaluateBuildPrereqs(skipDatasources bool) hcl.Diagnostics {
diff --git a/packer_test/dag_tests/malformed_dep_test.go b/packer_test/dag_tests/malformed_dep_test.go
new file mode 100644
index 000000000..ba3a1a63b
--- /dev/null
+++ b/packer_test/dag_tests/malformed_dep_test.go
@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/packer/packer_test/common/check"
+)
+
+type malformedDepTestCase struct {
+	name          string
+	command       string
+	templatePath  string
+	useSequential bool
+}
+
+func genMalformedDepTestCases() []malformedDepTestCase {
+	retVals := []malformedDepTestCase{}
+
+	for _, cmd := range []string{"build", "validate"} {
+		for _, template := range []string{"./templates/malformed_data_dep.pkr.hcl", "./templates/malformed_local_dep.pkr.hcl"} {
+			for _, seq := range []bool{true, false} {
+				retVals = append(retVals, malformedDepTestCase{
+					name: fmt.Sprintf("Malformed dep packer %s --use-sequential-evaluation=%t %s",
+						cmd, seq, template),
+					command:       cmd,
+					templatePath:  template,
+					useSequential: seq,
+				})
+			}
+		}
+	}
+
+	return retVals
+}
+
+func (ts *PackerDAGTestSuite) TestMalformedDependency() {
+	pluginDir := ts.MakePluginDir()
+	defer pluginDir.Cleanup()
+
+	for _, tc := range genMalformedDepTestCases() {
+		ts.Run(tc.name, func() {
+			ts.PackerCommand().UsePluginDir(pluginDir).
+				SetArgs(tc.command,
+					fmt.Sprintf("--use-sequential-evaluation=%t", tc.useSequential),
+					tc.templatePath).
+				Assert(check.MustFail())
+		})
+	}
+}
diff --git a/packer_test/dag_tests/templates/malformed_data_dep.pkr.hcl b/packer_test/dag_tests/templates/malformed_data_dep.pkr.hcl
new file mode 100644
index 000000000..d0fc29245
--- /dev/null
+++ b/packer_test/dag_tests/templates/malformed_data_dep.pkr.hcl
@@ -0,0 +1,8 @@
+data "http" "trusted_ca_certificates" {
+  method = "GET"
+  url    = "http://example.com/ca-bundle.crt"
+}
+
+locals {
+  test = data.trusted_ca_certificates.url
+}
diff --git a/packer_test/dag_tests/templates/malformed_local_dep.pkr.hcl b/packer_test/dag_tests/templates/malformed_local_dep.pkr.hcl
new file mode 100644
index 000000000..4b9b91ab2
--- /dev/null
+++ b/packer_test/dag_tests/templates/malformed_local_dep.pkr.hcl
@@ -0,0 +1,4 @@
+data "http" "trusted_ca_certificates" {
+  method = "GET"
+  url    = local.no_dep
+}