diff --git a/test/parallel/test-zlib-dictionary-fail.js b/test/parallel/test-zlib-dictionary-fail.js
index 269b733e2c6d56..9546954841f4b1 100644
--- a/test/parallel/test-zlib-dictionary-fail.js
+++ b/test/parallel/test-zlib-dictionary-fail.js
@@ -53,7 +53,7 @@ const input = Buffer.from([0x78, 0xBB, 0x04, 0x09, 0x01, 0xA5]);
   stream.on('error', common.mustCall(function(err) {
     // It's not possible to separate invalid dict and invalid data when using
     // the raw format
-    assert.match(err.message, /invalid/);
+    assert.match(err.message, /(invalid|Operation-Ending-Supplemental Code is 0x12)/);
   }));
 
   stream.write(input);
diff --git a/test/parallel/test-zlib-flush-drain-longblock.js b/test/parallel/test-zlib-flush-drain-longblock.js
index 94d1d9d04d9369..e2f56ec76292bf 100644
--- a/test/parallel/test-zlib-flush-drain-longblock.js
+++ b/test/parallel/test-zlib-flush-drain-longblock.js
@@ -16,7 +16,7 @@ zipper.write('A'.repeat(17000));
 zipper.flush();
 
 let received = 0;
-unzipper.on('data', common.mustCall((d) => {
+unzipper.on('data', common.mustCallAtLeast((d) => {
   received += d.length;
 }, 2));
 
diff --git a/test/parallel/test-zlib-from-string.js b/test/parallel/test-zlib-from-string.js
index fa96623536d279..92b6f8664666a0 100644
--- a/test/parallel/test-zlib-from-string.js
+++ b/test/parallel/test-zlib-from-string.js
@@ -55,7 +55,9 @@ const expectedBase64Gzip = 'H4sIAAAAAAAAA11RS05DMQy8yhzg6d2BPSAkJPZu4laWkjiN4' +
                            'sHnHNzRtagj5AQAA';
 
 zlib.deflate(inputString, common.mustCall((err, buffer) => {
-  assert.strictEqual(buffer.toString('base64'), expectedBase64Deflate);
+  zlib.inflate(buffer, common.mustCall((err, inflated) => {
+    assert.strictEqual(inflated.toString(), inputString);
+  }));
 }));
 
 zlib.gzip(inputString, common.mustCall((err, buffer) => {