diff --git a/libsolidity/analysis/DeclarationTypeChecker.cpp b/libsolidity/analysis/DeclarationTypeChecker.cpp
index f67d7d501..b015939e2 100644
--- a/libsolidity/analysis/DeclarationTypeChecker.cpp
+++ b/libsolidity/analysis/DeclarationTypeChecker.cpp
@@ -253,12 +253,13 @@ void DeclarationTypeChecker::endVisit(Mapping const& _mapping)
 		{
 			case Type::Category::Enum:
 			case Type::Category::Contract:
+			case Type::Category::UserDefinedValueType:
 				break;
 			default:
 				m_errorReporter.fatalTypeError(
 					7804_error,
 					typeName->location(),
-					"Only elementary types, contract types or enums are allowed as mapping keys."
+					"Only elementary types, user defined value types, contract types or enums are allowed as mapping keys."
 				);
 				break;
 		}
diff --git a/test/libsolidity/semanticTests/userDefinedValueType/mapping_key.sol b/test/libsolidity/semanticTests/userDefinedValueType/mapping_key.sol
new file mode 100644
index 000000000..e698308b4
--- /dev/null
+++ b/test/libsolidity/semanticTests/userDefinedValueType/mapping_key.sol
@@ -0,0 +1,18 @@
+type MyInt is int;
+contract C {
+    mapping(MyInt => int) public m;
+    function set(MyInt key, int value) external {
+        m[key] = value;
+    }
+    function set_unwrapped(int key, int value) external {
+        m[MyInt.wrap(key)] = value;
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// set(int256,int256): 1, 1 ->
+// m(int256): 1 -> 1
+// set_unwrapped(int256,int256): 1, 2 ->
+// m(int256): 1 -> 2
+// m(int256): 2 -> 0
diff --git a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_2.sol b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_2.sol
index 71063e34e..68aa61a41 100644
--- a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_2.sol
+++ b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_2.sol
@@ -5,4 +5,4 @@ contract c {
 	mapping(S => uint) data;
 }
 // ----
-// TypeError 7804: (47-48): Only elementary types, contract types or enums are allowed as mapping keys.
+// TypeError 7804: (47-48): Only elementary types, user defined value types, contract types or enums are allowed as mapping keys.
diff --git a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_3.sol b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_3.sol
index 34f0e82b3..991f2b622 100644
--- a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_3.sol
+++ b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_3.sol
@@ -5,4 +5,4 @@ contract c {
 	mapping(S => uint) data;
 }
 // ----
-// TypeError 7804: (49-50): Only elementary types, contract types or enums are allowed as mapping keys.
+// TypeError 7804: (49-50): Only elementary types, user defined value types, contract types or enums are allowed as mapping keys.
diff --git a/test/libsolidity/syntaxTests/types/struct_mapping_recursion.sol b/test/libsolidity/syntaxTests/types/struct_mapping_recursion.sol
index 5dc39266f..be4e1dde0 100644
--- a/test/libsolidity/syntaxTests/types/struct_mapping_recursion.sol
+++ b/test/libsolidity/syntaxTests/types/struct_mapping_recursion.sol
@@ -6,4 +6,4 @@ contract C {
 	function g (S calldata) external view {}
  }
 // ----
-// TypeError 7804: (56-57): Only elementary types, contract types or enums are allowed as mapping keys.
+// TypeError 7804: (56-57): Only elementary types, user defined value types, contract types or enums are allowed as mapping keys.
diff --git a/test/libsolidity/syntaxTests/userDefinedValueType/mapping_key.sol b/test/libsolidity/syntaxTests/userDefinedValueType/mapping_key.sol
new file mode 100644
index 000000000..ae83ae4c7
--- /dev/null
+++ b/test/libsolidity/syntaxTests/userDefinedValueType/mapping_key.sol
@@ -0,0 +1,4 @@
+type MyInt is int;
+contract C {
+    mapping(MyInt => int) m;
+}