diff --git a/Readme.md b/Readme.md
index a4fa9bd..12de65e 100644
--- a/Readme.md
+++ b/Readme.md
@@ -16,7 +16,12 @@ This Terraform module provides resources to manage GitLab groups, projects, inte
 ## Requirements
 
 - Terraform 1.8.0 or higher.
-- GitLab Provider for Terraform 19.0.0 or higher. See [docs/UPGRADE-2.0.md](docs/UPGRADE-2.0.md) if upgrading from a 18.x-based release of this module.
+- GitLab Provider for Terraform 19.5.0. The module pins this exact version. After you change the module version, run `terraform init -upgrade`. See [docs/UPGRADE-2.0.md](docs/UPGRADE-2.0.md) if upgrading from a 18.x-based release of this module.
+
+## Notes
+
+- `pipeline_schedules[*].ref` accepts a short branch name (`main`) or a full ref (`refs/heads/main`, `refs/tags/v1.0.0`). The module changes a short name to `refs/heads/<name>`. For a tag, use the full ref.
+- The provider deprecated the `push_rules` block of `gitlab_project` in 19.4.1 and removes it in 20.0. The module uses this block for project `push_rules`, and the plan shows a deprecation warning.
 
 ## Usage
 
diff --git a/main.tf b/main.tf
index e514d69..154fc1f 100644
--- a/main.tf
+++ b/main.tf
@@ -1284,13 +1284,16 @@ resource "gitlab_pipeline_schedule" "this" {
         project_name      = project.name
         project_namespace = project.namespace
         pipeline_schedule = pipeline
+        # Provider >= 19.4.1 accepts only a full ref. A short ref is a branch name.
+        # The for_each key keeps the ref as written, so the addresses do not change.
+        full_ref = startswith(pipeline.ref, "refs/") ? pipeline.ref : "refs/heads/${pipeline.ref}"
       }
     }
   ]...)
 
   project        = gitlab_project.this["${each.value.project_namespace}/${each.value.project_name}"].id
   description    = each.value.pipeline_schedule.description
-  ref            = each.value.pipeline_schedule.ref
+  ref            = each.value.full_ref
   cron           = each.value.pipeline_schedule.cron
   active         = lookup(each.value.pipeline_schedule, "active", false)
   cron_timezone  = lookup(each.value.pipeline_schedule, "cron_timezone", "UTC")
diff --git a/tests/pipeline_schedules.tftest.hcl b/tests/pipeline_schedules.tftest.hcl
new file mode 100644
index 0000000..f9fc5b9
--- /dev/null
+++ b/tests/pipeline_schedules.tftest.hcl
@@ -0,0 +1,38 @@
+# Unit tests for the ref of pipeline schedules. They use a mock provider and do not call GitLab.
+
+mock_provider "gitlab" {}
+
+variables {
+  gitlab_groups = []
+  gitlab_projects = [
+    {
+      name      = "api"
+      namespace = "alpha"
+      create    = true
+      settings = {
+        pipeline_schedules = [
+          { description = "nightly", ref = "main", cron = "0 1 * * *" },
+          { description = "release", ref = "refs/tags/v1.0.0", cron = "0 2 * * *" },
+        ]
+      }
+    },
+  ]
+}
+
+run "short_ref_becomes_a_full_branch_ref" {
+  command = plan
+
+  assert {
+    condition     = gitlab_pipeline_schedule.this["alpha-api-main-nightly"].ref == "refs/heads/main"
+    error_message = "A short ref must become refs/heads/<ref>, and the key must keep the ref as written."
+  }
+}
+
+run "full_ref_does_not_change" {
+  command = plan
+
+  assert {
+    condition     = gitlab_pipeline_schedule.this["alpha-api-refs/tags/v1.0.0-release"].ref == "refs/tags/v1.0.0"
+    error_message = "A full ref must not change."
+  }
+}
diff --git a/versions.tf b/versions.tf
index 2a73634..081726b 100644
--- a/versions.tf
+++ b/versions.tf
@@ -2,7 +2,7 @@ terraform {
   required_providers {
     gitlab = {
       source  = "gitlabhq/gitlab"
-      version = "= 19.1.0"
+      version = "= 19.5.0"
     }
   }
   required_version = ">= 1.8.0"