diff --git a/checks.go b/checks.go
index 1a4c8cc..558cb29 100644
--- a/checks.go
+++ b/checks.go
@@ -92,7 +92,7 @@
 	//
 	// InstanceKey will be empty if there was no foreach or count argument
 	// defined on the containing object.
-	InstanceKey string `json:"instance_key,omitempty"`
+	InstanceKey interface{} `json:"instance_key,omitempty"`
 }
 
 // CheckResultStatic is the container for a "checkable object".
diff --git a/parse_test.go b/parse_test.go
index 79c9a66..137d475 100644
--- a/parse_test.go
+++ b/parse_test.go
@@ -31,6 +31,12 @@
 			continue
 		}
 
+		// Skip this directory as this is a unique test that only tests a subset
+		// of attributes for a plan. The fixture is not entirely valid, but that's okay.
+		if e.Name() == "has_checks" {
+			continue
+		}
+
 		t.Run(e.Name(), func(t *testing.T) {
 			expected, err := ioutil.ReadFile(filepath.Join(testFixtureDir, e.Name(), filename))
 			if err != nil {
diff --git a/plan_test.go b/plan_test.go
index c74826d..035cd4a 100644
--- a/plan_test.go
+++ b/plan_test.go
@@ -6,6 +6,7 @@
 import (
 	"encoding/json"
 	"os"
+	"reflect"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -65,3 +66,36 @@
 		t.Fatalf("unexpected variables: %s", diff)
 	}
 }
+
+func TestPlan_withChecks(t *testing.T) {
+	f, err := os.Open("testdata/has_checks/plan.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	var plan *Plan
+	if err := json.NewDecoder(f).Decode(&plan); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := plan.Validate(); err != nil {
+		t.Fatal(err)
+	}
+
+	if len(plan.Checks) == 0 {
+		t.Fatal("expected checks to not be empty")
+	}
+
+	for _, c := range plan.Checks {
+		for _, instance := range c.Instances {
+			k := reflect.TypeOf(instance.Address.InstanceKey).Kind()
+			switch k {
+			case reflect.Int, reflect.Float32, reflect.Float64, reflect.String:
+				t.Log("instance key is a valid type")
+			default:
+				t.Fatalf("unexpected type %s, expected string or int", k.String())
+			}
+		}
+	}
+}
diff --git a/testdata/has_checks/plan.json b/testdata/has_checks/plan.json
new file mode 100644
index 0000000..4c45605
--- /dev/null
+++ b/testdata/has_checks/plan.json
@@ -0,0 +1 @@
+{"format_version":"1.1","terraform_version":"1.5.0","planned_values":{"root_module":{"resources":[{"address":"null_resource.foo","mode":"managed","type":"null_resource","name":"foo","provider_name":"registry.terraform.io/hashicorp/null","schema_version":0,"values":{"triggers":null},"sensitive_values":{}}]}},"resource_changes":[{"address":"null_resource.foo","mode":"managed","type":"null_resource","name":"foo","provider_name":"registry.terraform.io/hashicorp/null","change":{"actions":["create"],"before":null,"after":{"triggers":null},"after_unknown":{"id":true},"before_sensitive":false,"after_sensitive":{}}}],"configuration":{"provider_config":{"null":{"name":"null","full_name":"registry.terraform.io/hashicorp/null"}},"root_module":{"resources":[{"address":"null_resource.foo","mode":"managed","type":"null_resource","name":"foo","provider_config_key":"null","schema_version":0}]}},"checks":[{"//":"EXPERIMENTAL: see docs for details","address":{"kind":"resource","mode":"managed","module":"module.foo.module.bar","name":"this","to_display":"module.foo.module.bar.foobar.this","type":"foobar"},"status":"pass","instances":[{"address":{"instance_key":0,"module":"module.foo.module.bar","to_display":"module.foo.module.bar.foobar.this[0]"},"status":"pass"}]},{"//":"EXPERIMENTAL: see docs for details","address":{"kind":"resource","mode":"managed","module":"module.foo.module.bar","name":"this","to_display":"module.foo.module.bar.foobar.this","type":"foobar"},"status":"pass"}]}