diff --git a/CHANGELOG.md b/CHANGELOG.md
index 63ecf75..5ca0313 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.3.7
+
+- Use a constant variable for the bytecode marker.
+
 ## 0.3.6
 
 - Emit a payable constructor always.
diff --git a/src/core.test.ts.md b/src/core.test.ts.md
index 8ba5905..58d6d37 100644
--- a/src/core.test.ts.md
+++ b/src/core.test.ts.md
@@ -15,7 +15,7 @@ Generated by [AVA](https://avajs.dev).
     import "../contracts/Excluded.sol";␊
     ␊
     contract $Excluded is Excluded {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -34,7 +34,7 @@ Generated by [AVA](https://avajs.dev).
     import "../contracts/Imported2.sol";␊
     ␊
     contract $NotImported is NotImported {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -43,7 +43,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Imported is Imported {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -65,7 +65,7 @@ Generated by [AVA](https://avajs.dev).
     import "../contracts/Imported2.sol";␊
     ␊
     contract $NotImported2 is NotImported2 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -74,7 +74,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Imported2 is Imported2 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -96,7 +96,7 @@ Generated by [AVA](https://avajs.dev).
     import "../contracts/Inheritance.sol";␊
     ␊
     contract $Parent1 is Parent1 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x) Parent1(x) payable {␊
         }␊
@@ -109,7 +109,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Parent2 is Parent2 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 y) Parent2(y) payable {␊
         }␊
@@ -118,7 +118,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Parent3 is Parent3 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 z) Parent3(z) payable {␊
         }␊
@@ -127,7 +127,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Child1 is Child1 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x) Parent1(x) payable {␊
         }␊
@@ -140,7 +140,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Child2 is Child2 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x, uint256 y) Parent1(x) Parent2(y) payable {␊
         }␊
@@ -153,7 +153,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Child3 is Child3 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x, uint256 y) Parent1(x) Parent2(y) payable {␊
         }␊
@@ -166,7 +166,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Child4 is Child4 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x, uint256 y, uint256 z, uint256 c) Parent1(x) Parent2(y) Parent3(z) Child4(c) payable {␊
         }␊
@@ -188,7 +188,7 @@ Generated by [AVA](https://avajs.dev).
     import "../contracts/Initializers.sol";␊
     ␊
     contract $Initializable is Initializable {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -197,7 +197,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $AU is AU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -218,7 +218,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $BU is BU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -247,7 +247,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $CU is CU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -284,7 +284,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $XU is XU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -305,7 +305,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $YU is YU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -334,7 +334,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $YUW is YUW {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x) YUW(x) payable {␊
         }␊
@@ -373,7 +373,7 @@ Generated by [AVA](https://avajs.dev).
     import "../contracts/Imported.sol";␊
     ␊
     contract $Foo is Foo {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         mapping(uint256 => S) internal $v_S;␊
     ␊
@@ -446,7 +446,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Bar is Bar {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         mapping(uint256 => S) internal $v_S;␊
     ␊
@@ -523,7 +523,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Lib {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         mapping(uint256 => S) internal $v_S;␊
     ␊
@@ -561,7 +561,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     abstract contract $Iface is Iface {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -570,7 +570,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     abstract contract $Abs is Abs {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -579,7 +579,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Concrete1 is Concrete1 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -588,7 +588,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Concrete2 is Concrete2 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -597,7 +597,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Types is Types {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         mapping(uint256 => mapping(uint256 => uint256)) internal $v_mapping_uint256_uint256_;␊
     ␊
@@ -620,7 +620,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $ConstructorStorageLocation is ConstructorStorageLocation {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(string memory name) ConstructorStorageLocation(name) payable {␊
         }␊
@@ -629,7 +629,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $ImplicitConstructor is ImplicitConstructor {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -638,7 +638,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Chained0 is Chained0 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -651,7 +651,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Chained1 is Chained1 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -664,7 +664,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $Chained2 is Chained2 {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -677,7 +677,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $WithVars is WithVars {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -718,7 +718,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $WithInternalReturns is WithInternalReturns {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         event return$incrementInternal(uint256 ret0);␊
     ␊
@@ -762,14 +762,14 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $HasReceiveFunction is HasReceiveFunction {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
     }␊
     ␊
     contract $ImportedChild is ImportedChild {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -793,7 +793,7 @@ Generated by [AVA](https://avajs.dev).
     import "../contracts/Initializers.sol";␊
     ␊
     contract $Initializable is Initializable {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor() payable {␊
         }␊
@@ -802,7 +802,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $AU is AU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 a) initializer payable {␊
             __A_init(a);␊
@@ -824,7 +824,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $BU is BU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 b) initializer payable {␊
             __B_init(b);␊
@@ -854,7 +854,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $CU is CU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 b) initializer payable {␊
             __B_init(b);␊
@@ -893,7 +893,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $XU is XU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x) initializer payable {␊
             __X_init(x);␊
@@ -915,7 +915,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $YU is YU {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x) initializer payable {␊
             __X_init(x);␊
@@ -946,7 +946,7 @@ Generated by [AVA](https://avajs.dev).
     }␊
     ␊
     contract $YUW is YUW {␊
-        bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";␊
+        bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";␊
     ␊
         constructor(uint256 x) YUW(x) initializer payable {␊
             __Y_init();␊
diff --git a/src/core.test.ts.snap b/src/core.test.ts.snap
index 85063b0..365b87d 100644
Binary files a/src/core.test.ts.snap and b/src/core.test.ts.snap differ
diff --git a/src/core.ts b/src/core.ts
index ce5661d..6bd241b 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -117,7 +117,7 @@ function getExposedContent(ast: SourceUnit, relativizePath: (p: string) => strin
 
         return [
           contractHeader.join(' '),
-          [`bytes32 public __hh_exposed_bytecode_marker = "hardhat-exposed";\n`],
+          [`bytes32 public constant __hh_exposed_bytecode_marker = "hardhat-exposed";\n`],
           spaceBetween(
             // slots for storage function parameters
             ...getAllStorageArguments(externalizableFunctions).map(a => [