diff --git a/internal/addrs/module_instance.go b/internal/addrs/module_instance.go
index 2eb57948d..21afcb077 100644
--- a/internal/addrs/module_instance.go
+++ b/internal/addrs/module_instance.go
@@ -275,6 +275,14 @@ func (m ModuleInstance) String() string {
 	return buf.String()
 }
 
+type moduleInstanceKey string
+
+func (m ModuleInstance) UniqueKey() UniqueKey {
+	return moduleInstanceKey(m.String())
+}
+
+func (mk moduleInstanceKey) uniqueKeySigil() {}
+
 // Equal returns true if the receiver and the given other value
 // contains the exact same parts.
 func (m ModuleInstance) Equal(o ModuleInstance) bool {
diff --git a/internal/addrs/resource.go b/internal/addrs/resource.go
index f22db05cb..a7b7ee308 100644
--- a/internal/addrs/resource.go
+++ b/internal/addrs/resource.go
@@ -292,6 +292,14 @@ func (r AbsResourceInstance) Less(o AbsResourceInstance) bool {
 	}
 }
 
+type absResourceInstanceKey string
+
+func (r AbsResourceInstance) UniqueKey() UniqueKey {
+	return absResourceInstanceKey(r.String())
+}
+
+func (r absResourceInstanceKey) uniqueKeySigil() {}
+
 func (r AbsResourceInstance) absMoveableSigil() {
 	// AbsResourceInstance is moveable
 }
diff --git a/internal/addrs/unique_key_test.go b/internal/addrs/unique_key_test.go
index 416899ca4..0926a0c37 100644
--- a/internal/addrs/unique_key_test.go
+++ b/internal/addrs/unique_key_test.go
@@ -46,6 +46,14 @@ func TestUniqueKeyer(t *testing.T) {
 			},
 			Key: IntKey(1),
 		},
+		RootModuleInstance,
+		RootModuleInstance.Child("foo", NoKey),
+		RootModuleInstance.ResourceInstance(
+			DataResourceMode,
+			"boop",
+			"beep",
+			NoKey,
+		),
 		Self,
 	}