diff --git a/src/datatypes/compiler-utils.js b/src/datatypes/compiler-utils.js
index 6625a51..c74afec 100644
--- a/src/datatypes/compiler-utils.js
+++ b/src/datatypes/compiler-utils.js
@@ -160,8 +160,11 @@ return (ctx.${type})(val, buffer, offset)
     }],
     mapper: ['parametrizable', (compiler, mapper) => {
       const mappings = JSON.stringify(swapMappings(mapper.mappings))
-      let code = `const mapped = ${mappings}[value]\n`
-      code += 'if (mapped === undefined) throw new Error(value + \' is not in the mappings value\')\n'
+      let code = `let mapped = ${mappings}[value]\n`
+      code += 'if (mapped === undefined) {\n'
+      code += '  if (typeof value !== \'number\') throw new Error(value + \' is not in the mappings value\')\n'
+      code += '  mapped = value\n'
+      code += '}\n'
       code += 'return ' + compiler.callType('mapped', mapper.type)
       return compiler.wrapCode(code)
     }]
@@ -215,8 +218,11 @@ return (ctx.${type})(val)
     }],
     mapper: ['parametrizable', (compiler, mapper) => {
       const mappings = JSON.stringify(swapMappings(mapper.mappings))
-      let code = `const mapped = ${mappings}[value]\n`
-      code += 'if (mapped === undefined) throw new Error(value + \' is not in the mappings value\')\n'
+      let code = `let mapped = ${mappings}[value]\n`
+      code += 'if (mapped === undefined) {\n'
+      code += '  if (typeof value !== \'number\') throw new Error(value + \' is not in the mappings value\')\n'
+      code += '  mapped = value\n'
+      code += '}\n'
       code += 'return ' + compiler.callType('mapped', mapper.type)
       return compiler.wrapCode(code)
     }]
diff --git a/test/misc.js b/test/misc.js
index 6877ba4..3ae1325 100644
--- a/test/misc.js
+++ b/test/misc.js
@@ -24,6 +24,12 @@ describe('mapper', () => {
       assert.throws(() => p.createPacketBuffer('name', 'nope'), /nope is not in the mappings value/)
     })
   }
+
+  // The compiled read returns the raw id for a value not in the mappings, so writing it back must work
+  it('writes a raw integer not in the mappings (compiled)', () => {
+    assert.deepStrictEqual(compiled.createPacketBuffer('name', 5), Buffer.from([5]))
+    assert.strictEqual(compiled.parsePacketBuffer('name', Buffer.from([5])).data, 5)
+  })
 })
 
 describe('bitflags', () => {