diff --git a/README.md b/README.md
index 9f297c85..73888604 100644
--- a/README.md
+++ b/README.md
@@ -46,12 +46,12 @@ Functional examples are included in the
 
 | Name | Description | Type | Default | Required |
 |------|-------------|:----:|:-----:|:-----:|
-| admins | IAM-style members who will be granted roles/storage.objectAdmin on all buckets. | list | `<list>` | no |
+| admins | IAM-style members who will be granted roles/storage.objectAdmin on all buckets. | list(string) | `<list>` | no |
 | bucket\_admins | Map of lowercase unprefixed name => comma-delimited IAM-style bucket admins. | map | `<map>` | no |
 | bucket\_creators | Map of lowercase unprefixed name => comma-delimited IAM-style bucket creators. | map | `<map>` | no |
 | bucket\_policy\_only | Disable ad-hoc ACLs on specified buckets. Defaults to true. Map of lowercase unprefixed name => boolean | map | `<map>` | no |
 | bucket\_viewers | Map of lowercase unprefixed name => comma-delimited IAM-style bucket viewers. | map | `<map>` | no |
-| creators | IAM-style members who will be granted roles/storage.objectCreators on all buckets. | list | `<list>` | no |
+| creators | IAM-style members who will be granted roles/storage.objectCreators on all buckets. | list(string) | `<list>` | no |
 | encryption\_key\_names | Optional map of lowercase unprefixed name => string, empty strings are ignored. | map | `<map>` | no |
 | force\_destroy | Optional map of lowercase unprefixed name => boolean, defaults to false. | map | `<map>` | no |
 | labels | Labels to be attached to the buckets | map | `<map>` | no |
@@ -60,12 +60,12 @@ Functional examples are included in the
 | names | Bucket name suffixes. | list(string) | n/a | yes |
 | prefix | Prefix used to generate the bucket name. | string | n/a | yes |
 | project\_id | Bucket project id. | string | n/a | yes |
-| set\_admin\_roles | Grant roles/storage.objectAdmin role to admins and bucket_admins. | string | `"false"` | no |
-| set\_creator\_roles | Grant roles/storage.objectCreator role to creators and bucket_creators. | string | `"false"` | no |
-| set\_viewer\_roles | Grant roles/storage.objectViewer role to viewers and bucket_viewers. | string | `"false"` | no |
+| set\_admin\_roles | Grant roles/storage.objectAdmin role to admins and bucket_admins. | bool | `"false"` | no |
+| set\_creator\_roles | Grant roles/storage.objectCreator role to creators and bucket_creators. | bool | `"false"` | no |
+| set\_viewer\_roles | Grant roles/storage.objectViewer role to viewers and bucket_viewers. | bool | `"false"` | no |
 | storage\_class | Bucket storage class. | string | `"MULTI_REGIONAL"` | no |
 | versioning | Optional map of lowercase unprefixed name => boolean, defaults to false. | map | `<map>` | no |
-| viewers | IAM-style members who will be granted roles/storage.objectViewer on all buckets. | list | `<list>` | no |
+| viewers | IAM-style members who will be granted roles/storage.objectViewer on all buckets. | list(string) | `<list>` | no |
 
 ## Outputs
 
diff --git a/variables.tf b/variables.tf
index 22570cdd..83851d12 100644
--- a/variables.tf
+++ b/variables.tf
@@ -16,10 +16,12 @@
 
 variable "project_id" {
   description = "Bucket project id."
+  type        = string
 }
 
 variable "prefix" {
   description = "Prefix used to generate the bucket name."
+  type        = string
 }
 
 variable "names" {
@@ -29,66 +31,79 @@ variable "names" {
 
 variable "location" {
   description = "Bucket location."
+  type        = string
   default     = "EU"
 }
 
 variable "storage_class" {
   description = "Bucket storage class."
+  type        = string
   default     = "MULTI_REGIONAL"
 }
 
 variable "force_destroy" {
   description = "Optional map of lowercase unprefixed name => boolean, defaults to false."
+  type        = map
   default     = {}
 }
 
 variable "versioning" {
   description = "Optional map of lowercase unprefixed name => boolean, defaults to false."
+  type        = map
   default     = {}
 }
 
 variable "encryption_key_names" {
   description = "Optional map of lowercase unprefixed name => string, empty strings are ignored."
+  type        = map
   default     = {}
 }
 
 variable "bucket_policy_only" {
   description = "Disable ad-hoc ACLs on specified buckets. Defaults to true. Map of lowercase unprefixed name => boolean"
+  type        = map
   default     = {}
 }
 
 variable "admins" {
   description = "IAM-style members who will be granted roles/storage.objectAdmin on all buckets."
+  type        = list(string)
   default     = []
 }
 
 variable "creators" {
   description = "IAM-style members who will be granted roles/storage.objectCreators on all buckets."
+  type        = list(string)
   default     = []
 }
 
 variable "viewers" {
   description = "IAM-style members who will be granted roles/storage.objectViewer on all buckets."
+  type        = list(string)
   default     = []
 }
 
 variable "bucket_admins" {
   description = "Map of lowercase unprefixed name => comma-delimited IAM-style bucket admins."
+  type        = map
   default     = {}
 }
 
 variable "bucket_creators" {
   description = "Map of lowercase unprefixed name => comma-delimited IAM-style bucket creators."
+  type        = map
   default     = {}
 }
 
 variable "bucket_viewers" {
   description = "Map of lowercase unprefixed name => comma-delimited IAM-style bucket viewers."
+  type        = map
   default     = {}
 }
 
 variable "labels" {
   description = "Labels to be attached to the buckets"
+  type        = map
   default     = {}
 }
 
@@ -96,16 +111,19 @@ variable "labels" {
 
 variable "set_admin_roles" {
   description = "Grant roles/storage.objectAdmin role to admins and bucket_admins."
+  type        = bool
   default     = false
 }
 
 variable "set_creator_roles" {
   description = "Grant roles/storage.objectCreator role to creators and bucket_creators."
+  type        = bool
   default     = false
 }
 
 variable "set_viewer_roles" {
   description = "Grant roles/storage.objectViewer role to viewers and bucket_viewers."
+  type        = bool
   default     = false
 }
 
@@ -117,6 +135,6 @@ variable "lifecycle_rules" {
     })
     condition = map(string)
   }))
-  default     = []
   description = "List of lifecycle rules to configure. Format is the same as described in provider documentation https://www.terraform.io/docs/providers/google/r/storage_bucket.html#lifecycle_rule except condition.matches_storage_class should be a comma delimited string."
+  default     = []
 }