diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8155507..2258483 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [3.18.1] - 2024-04-10
+  - mprv should not be implemented when U mode is absent.
+
 ## [3.18.0] - 2024-04-02
   - mabi generation to account for E extension
 
diff --git a/riscv_config/__init__.py b/riscv_config/__init__.py
index 4a2c842..3dabce5 100644
--- a/riscv_config/__init__.py
+++ b/riscv_config/__init__.py
@@ -1,4 +1,4 @@
 from pkgutil import extend_path
 __path__ = extend_path(__path__, __name__)
-__version__ = '3.18.0'
+__version__ = '3.18.1'
 
diff --git a/riscv_config/schemas/schema_isa.yaml b/riscv_config/schemas/schema_isa.yaml
index d7d2960..981ee62 100644
--- a/riscv_config/schemas/schema_isa.yaml
+++ b/riscv_config/schemas/schema_isa.yaml
@@ -760,11 +760,11 @@ hart_schema:
                     warl:
                        dependency_fields: []
                        legal:
-                         - mprv[0] in [0x0]
+                         - mprv[0] in [0x0, 0x1]
                        wr_illegal:
                          - unchanged
               default: {implemented: false}
-              check_with: s_check
+              check_with: u_check
             sum:
               type: dict
               schema:
@@ -1175,11 +1175,11 @@ hart_schema:
                     warl:
                        dependency_fields: []
                        legal:
-                         - mprv[0] in [0x0]
+                         - mprv[0] in [0x0, 0x1]
                        wr_illegal:
                          - unchanged
               default: {implemented: false}
-              check_with: s_check
+              check_with: u_check
             sum:
               type: dict
               schema:
diff --git a/setup.cfg b/setup.cfg
index 45a8085..2b571e4 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 3.18.0
+current_version = 3.18.1
 commit = True
 tag = True