diff --git a/test/parallel/test-zlib-const.js b/test/parallel/test-zlib-const.js
index e4c673aff0..d25a1ca6be 100644
--- a/test/parallel/test-zlib-const.js
+++ b/test/parallel/test-zlib-const.js
@@ -4,14 +4,35 @@ const assert = require('assert');
 
 const zlib = require('zlib');
 
-assert.strictEqual(zlib.constants.Z_OK, 0, 'Z_OK should be 0');
+assert.strictEqual(zlib.constants.Z_OK, 0,
+                   [
+                     'Expected Z_OK to be 0;',
+                     `got ${zlib.constants.Z_OK}`
+                   ].join(' '));
 zlib.constants.Z_OK = 1;
-assert.strictEqual(zlib.constants.Z_OK, 0, 'Z_OK should be 0');
+assert.strictEqual(zlib.constants.Z_OK, 0,
+                   [
+                     'Z_OK should be immutable.',
+                     `Expected to get 0, got ${zlib.constants.Z_OK}`
+                   ].join(' '));
 
-assert.strictEqual(zlib.codes.Z_OK, 0, 'Z_OK should be 0');
+assert.strictEqual(zlib.codes.Z_OK, 0,
+                   `Expected Z_OK to be 0; got ${zlib.codes.Z_OK}`);
 zlib.codes.Z_OK = 1;
-assert.strictEqual(zlib.codes.Z_OK, 0, 'zlib.codes.Z_OK should be 0');
+assert.strictEqual(zlib.codes.Z_OK, 0,
+                   [
+                     'Z_OK should be immutable.',
+                     `Expected to get 0, got ${zlib.codes.Z_OK}`
+                   ].join(' '));
 zlib.codes = { Z_OK: 1 };
-assert.strictEqual(zlib.codes.Z_OK, 0, 'zlib.codes.Z_OK should be 0');
+assert.strictEqual(zlib.codes.Z_OK, 0,
+                   [
+                     'Z_OK should be immutable.',
+                     `Expected to get 0, got ${zlib.codes.Z_OK}`
+                   ].join(' '));
 
-assert.ok(Object.isFrozen(zlib.codes), 'zlib.codes should be frozen');
+assert.ok(Object.isFrozen(zlib.codes),
+          [
+            'Expected zlib.codes to be frozen, but Object.isFrozen',
+            `returned ${Object.isFrozen(zlib.codes)}`
+          ].join(' '));