diff --git a/README.md b/README.md
index fbbb371..f2548e9 100644
--- a/README.md
+++ b/README.md
@@ -53,7 +53,7 @@ Functional examples are included in the
 | members | Artifact Registry Reader and Writer roles for Users/SAs. Key names must be readers and/or writers | `map(list(string))` | `{}` | no |
 | mode | The mode configures the repository to serve artifacts from different sources. Default value is STANDARD\_REPOSITORY. Possible values are: STANDARD\_REPOSITORY, VIRTUAL\_REPOSITORY, REMOTE\_REPOSITORY | `string` | `"STANDARD_REPOSITORY"` | no |
 | project\_id | The project ID to create the repository | `string` | n/a | yes |
-| remote\_repository\_config | Configuration specific for a Remote Repository. | <pre>object({<br>    description                 = optional(string)<br>    disable_upstream_validation = optional(bool, true)<br>    upstream_credentials = optional(object({<br>      username                = string<br>      password_secret_version = string<br>    }), null)<br>    apt_repository = optional(object({<br>      public_repository = optional(object({<br>        repository_base = string<br>        repository_path = string<br>      }), null)<br>    }), null)<br>    docker_repository = optional(object({<br>      public_repository = optional(string, "DOCKER_HUB")<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    maven_repository = optional(object({<br>      public_repository = optional(string, "MAVEN_CENTRAL")<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    npm_repository = optional(object({<br>      public_repository = optional(string, "NPMJS")<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    python_repository = optional(object({<br>      public_repository = optional(string, "PYPI")<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    yum_repository = optional(object({<br>      public_repository = optional(object({<br>        repository_base = string<br>        repository_path = string<br>      }), null)<br>    }), null)<br>  })</pre> | `null` | no |
+| remote\_repository\_config | Configuration specific for a Remote Repository. | <pre>object({<br>    description                 = optional(string)<br>    disable_upstream_validation = optional(bool, true)<br>    upstream_credentials = optional(object({<br>      username                = string<br>      password_secret_version = string<br>    }), null)<br>    apt_repository = optional(object({<br>      public_repository = optional(object({<br>        repository_base = string<br>        repository_path = string<br>      }), null)<br>    }), null)<br>    docker_repository = optional(object({<br>      public_repository = optional(string)<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    maven_repository = optional(object({<br>      public_repository = optional(string)<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    npm_repository = optional(object({<br>      public_repository = optional(string)<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    python_repository = optional(object({<br>      public_repository = optional(string)<br>      custom_repository = optional(object({<br>        uri = string<br>      }), null)<br>    }), null)<br>    yum_repository = optional(object({<br>      public_repository = optional(object({<br>        repository_base = string<br>        repository_path = string<br>      }), null)<br>    }), null)<br>  })</pre> | `null` | no |
 | repository\_id | The repository name | `string` | n/a | yes |
 | virtual\_repository\_config | Configuration specific for a Virtual Repository. | <pre>object({<br>    upstream_policies = optional(list(object({<br>      id         = string<br>      repository = string<br>      priority   = number<br>    })), null)<br>  })</pre> | `null` | no |
 | vpcsc\_policy | The VPC SC policy for project and location. Possible values are: DENY, ALLOW | `string` | `"ALLOW"` | no |
diff --git a/docs/upgrading_to_v0.3.0.md b/docs/upgrading_to_v0.3.0.md
new file mode 100644
index 0000000..a1cbcbf
--- /dev/null
+++ b/docs/upgrading_to_v0.3.0.md
@@ -0,0 +1,31 @@
+# Upgrading to v0.3.0
+
+The v0.3.0 release of **terraform-google-artifact-registry** is a backwards
+incompatible release.
+
+### Defaults for Public Repositories
+
+Previously, this module provided defaults that pointed at well-known public
+repositories. Previously, for example, you could specify remote repository
+configuration for Docker Hub like so:
+
+```
+remote_repository_config = {
+  docker_repository = {}
+}
+```
+
+And you would get a remote repository configuration that would point to Docker
+Hub. Now, you have to explicitly specify that you want Docker Hub like so:
+
+```
+remote_repository_config = {
+  docker_repository = {
+    public_repository = "DOCKER_HUB"
+  }
+}
+```
+
+This change was made because the previous behavior of defaulting these to
+well-known values turned out to be incompatible with specifying custom
+repository options via the `custom_repository` argument.
diff --git a/variables.tf b/variables.tf
index e464151..2213f9c 100644
--- a/variables.tf
+++ b/variables.tf
@@ -102,25 +102,25 @@ variable "remote_repository_config" {
       }), null)
     }), null)
     docker_repository = optional(object({
-      public_repository = optional(string, "DOCKER_HUB")
+      public_repository = optional(string)
       custom_repository = optional(object({
         uri = string
       }), null)
     }), null)
     maven_repository = optional(object({
-      public_repository = optional(string, "MAVEN_CENTRAL")
+      public_repository = optional(string)
       custom_repository = optional(object({
         uri = string
       }), null)
     }), null)
     npm_repository = optional(object({
-      public_repository = optional(string, "NPMJS")
+      public_repository = optional(string)
       custom_repository = optional(object({
         uri = string
       }), null)
     }), null)
     python_repository = optional(object({
-      public_repository = optional(string, "PYPI")
+      public_repository = optional(string)
       custom_repository = optional(object({
         uri = string
       }), null)