diff --git a/README.md b/README.md
index 60931a99af..4c15b0f311 100644
--- a/README.md
+++ b/README.md
@@ -172,7 +172,7 @@ In either case, upgrading to module version `v1.0.0` will trigger a recreation o
 | skip\_provisioners | Flag to skip all local-exec provisioners. It breaks `stub_domains` and `upstream_nameservers` variables functionality. | bool | `"false"` | no |
 | stub\_domains | Map of stub domains and their resolvers to forward DNS queries for a certain domain to an external DNS server | map(list(string)) | `<map>` | no |
 | subnetwork | The subnetwork to host the cluster in (required) | string | n/a | yes |
-| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list | `<list>` | no |
+| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list(string) | `<list>` | no |
 | zones | The zones to host the cluster in (optional if regional cluster / required if zonal) | list(string) | `<list>` | no |
 
 ## Outputs
diff --git a/autogen/variables.tf.tmpl b/autogen/variables.tf.tmpl
index 71f2c65413..5b87f08e05 100644
--- a/autogen/variables.tf.tmpl
+++ b/autogen/variables.tf.tmpl
@@ -217,7 +217,7 @@ variable "stub_domains" {
 }
 
 variable "upstream_nameservers" {
-  type        = "list"
+  type        = list(string)
   description = "If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf"
   default     = []
 }
diff --git a/modules/beta-private-cluster-update-variant/README.md b/modules/beta-private-cluster-update-variant/README.md
index 2f52021bd7..22227f6a1e 100644
--- a/modules/beta-private-cluster-update-variant/README.md
+++ b/modules/beta-private-cluster-update-variant/README.md
@@ -200,7 +200,7 @@ In either case, upgrading to module version `v1.0.0` will trigger a recreation o
 | skip\_provisioners | Flag to skip all local-exec provisioners. It breaks `stub_domains` and `upstream_nameservers` variables functionality. | bool | `"false"` | no |
 | stub\_domains | Map of stub domains and their resolvers to forward DNS queries for a certain domain to an external DNS server | map(list(string)) | `<map>` | no |
 | subnetwork | The subnetwork to host the cluster in (required) | string | n/a | yes |
-| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list | `<list>` | no |
+| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list(string) | `<list>` | no |
 | zones | The zones to host the cluster in (optional if regional cluster / required if zonal) | list(string) | `<list>` | no |
 
 ## Outputs
diff --git a/modules/beta-private-cluster-update-variant/variables.tf b/modules/beta-private-cluster-update-variant/variables.tf
index 890598553e..0f581e56cc 100644
--- a/modules/beta-private-cluster-update-variant/variables.tf
+++ b/modules/beta-private-cluster-update-variant/variables.tf
@@ -215,7 +215,7 @@ variable "stub_domains" {
 }
 
 variable "upstream_nameservers" {
-  type        = "list"
+  type        = list(string)
   description = "If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf"
   default     = []
 }
diff --git a/modules/beta-private-cluster/README.md b/modules/beta-private-cluster/README.md
index a60877eca3..c5c6b079ef 100644
--- a/modules/beta-private-cluster/README.md
+++ b/modules/beta-private-cluster/README.md
@@ -200,7 +200,7 @@ In either case, upgrading to module version `v1.0.0` will trigger a recreation o
 | skip\_provisioners | Flag to skip all local-exec provisioners. It breaks `stub_domains` and `upstream_nameservers` variables functionality. | bool | `"false"` | no |
 | stub\_domains | Map of stub domains and their resolvers to forward DNS queries for a certain domain to an external DNS server | map(list(string)) | `<map>` | no |
 | subnetwork | The subnetwork to host the cluster in (required) | string | n/a | yes |
-| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list | `<list>` | no |
+| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list(string) | `<list>` | no |
 | zones | The zones to host the cluster in (optional if regional cluster / required if zonal) | list(string) | `<list>` | no |
 
 ## Outputs
diff --git a/modules/beta-private-cluster/variables.tf b/modules/beta-private-cluster/variables.tf
index 890598553e..0f581e56cc 100644
--- a/modules/beta-private-cluster/variables.tf
+++ b/modules/beta-private-cluster/variables.tf
@@ -215,7 +215,7 @@ variable "stub_domains" {
 }
 
 variable "upstream_nameservers" {
-  type        = "list"
+  type        = list(string)
   description = "If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf"
   default     = []
 }
diff --git a/modules/beta-public-cluster/README.md b/modules/beta-public-cluster/README.md
index 00da4429f2..b0e2cfc85d 100644
--- a/modules/beta-public-cluster/README.md
+++ b/modules/beta-public-cluster/README.md
@@ -191,7 +191,7 @@ In either case, upgrading to module version `v1.0.0` will trigger a recreation o
 | skip\_provisioners | Flag to skip all local-exec provisioners. It breaks `stub_domains` and `upstream_nameservers` variables functionality. | bool | `"false"` | no |
 | stub\_domains | Map of stub domains and their resolvers to forward DNS queries for a certain domain to an external DNS server | map(list(string)) | `<map>` | no |
 | subnetwork | The subnetwork to host the cluster in (required) | string | n/a | yes |
-| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list | `<list>` | no |
+| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list(string) | `<list>` | no |
 | zones | The zones to host the cluster in (optional if regional cluster / required if zonal) | list(string) | `<list>` | no |
 
 ## Outputs
diff --git a/modules/beta-public-cluster/variables.tf b/modules/beta-public-cluster/variables.tf
index 717cd8d3c7..e27a7d0414 100644
--- a/modules/beta-public-cluster/variables.tf
+++ b/modules/beta-public-cluster/variables.tf
@@ -215,7 +215,7 @@ variable "stub_domains" {
 }
 
 variable "upstream_nameservers" {
-  type        = "list"
+  type        = list(string)
   description = "If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf"
   default     = []
 }
diff --git a/modules/private-cluster-update-variant/README.md b/modules/private-cluster-update-variant/README.md
index 37f95ccf7d..1786d3b46c 100644
--- a/modules/private-cluster-update-variant/README.md
+++ b/modules/private-cluster-update-variant/README.md
@@ -181,7 +181,7 @@ In either case, upgrading to module version `v1.0.0` will trigger a recreation o
 | skip\_provisioners | Flag to skip all local-exec provisioners. It breaks `stub_domains` and `upstream_nameservers` variables functionality. | bool | `"false"` | no |
 | stub\_domains | Map of stub domains and their resolvers to forward DNS queries for a certain domain to an external DNS server | map(list(string)) | `<map>` | no |
 | subnetwork | The subnetwork to host the cluster in (required) | string | n/a | yes |
-| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list | `<list>` | no |
+| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list(string) | `<list>` | no |
 | zones | The zones to host the cluster in (optional if regional cluster / required if zonal) | list(string) | `<list>` | no |
 
 ## Outputs
diff --git a/modules/private-cluster-update-variant/variables.tf b/modules/private-cluster-update-variant/variables.tf
index f4fbe9fdf1..82c268aecf 100644
--- a/modules/private-cluster-update-variant/variables.tf
+++ b/modules/private-cluster-update-variant/variables.tf
@@ -204,7 +204,7 @@ variable "stub_domains" {
 }
 
 variable "upstream_nameservers" {
-  type        = "list"
+  type        = list(string)
   description = "If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf"
   default     = []
 }
diff --git a/modules/private-cluster/README.md b/modules/private-cluster/README.md
index adbb3b8042..0f5c3df935 100644
--- a/modules/private-cluster/README.md
+++ b/modules/private-cluster/README.md
@@ -181,7 +181,7 @@ In either case, upgrading to module version `v1.0.0` will trigger a recreation o
 | skip\_provisioners | Flag to skip all local-exec provisioners. It breaks `stub_domains` and `upstream_nameservers` variables functionality. | bool | `"false"` | no |
 | stub\_domains | Map of stub domains and their resolvers to forward DNS queries for a certain domain to an external DNS server | map(list(string)) | `<map>` | no |
 | subnetwork | The subnetwork to host the cluster in (required) | string | n/a | yes |
-| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list | `<list>` | no |
+| upstream\_nameservers | If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf | list(string) | `<list>` | no |
 | zones | The zones to host the cluster in (optional if regional cluster / required if zonal) | list(string) | `<list>` | no |
 
 ## Outputs
diff --git a/modules/private-cluster/variables.tf b/modules/private-cluster/variables.tf
index f4fbe9fdf1..82c268aecf 100644
--- a/modules/private-cluster/variables.tf
+++ b/modules/private-cluster/variables.tf
@@ -204,7 +204,7 @@ variable "stub_domains" {
 }
 
 variable "upstream_nameservers" {
-  type        = "list"
+  type        = list(string)
   description = "If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf"
   default     = []
 }
diff --git a/variables.tf b/variables.tf
index 03dc33b814..b9fdf45738 100644
--- a/variables.tf
+++ b/variables.tf
@@ -204,7 +204,7 @@ variable "stub_domains" {
 }
 
 variable "upstream_nameservers" {
-  type        = "list"
+  type        = list(string)
   description = "If specified, the values replace the nameservers taken by default from the node’s /etc/resolv.conf"
   default     = []
 }