diff --git a/src/workerd/api/node/tests/zlib-zstd-nodejs-test.js b/src/workerd/api/node/tests/zlib-zstd-nodejs-test.js
index 3fcff0eb5d2..fcf20c7b974 100644
--- a/src/workerd/api/node/tests/zlib-zstd-nodejs-test.js
+++ b/src/workerd/api/node/tests/zlib-zstd-nodejs-test.js
@@ -3,6 +3,7 @@
 //     https://opensource.org/licenses/Apache-2.0
 import assert from 'node:assert';
 import { Buffer } from 'node:buffer';
+import { randomBytes } from 'node:crypto';
 import zlib from 'node:zlib';
 
 // Basic sync compress/decompress test
@@ -99,6 +100,20 @@ export const zstdLargeDataTest = {
 
     const decompressed = zlib.zstdDecompressSync(compressed);
     assert(input.equals(decompressed), 'Large data round-trip should match');
+
+    // workerd routes randomBytes() through getRandomValues(), which is capped at 64KiB per call.
+    const randomInput = Buffer.concat([
+      randomBytes(64 * 1024),
+      randomBytes(36 * 1024),
+    ]);
+    const randomCompressed = zlib.zstdCompressSync(randomInput);
+    assert(Buffer.isBuffer(randomCompressed), 'Random compressed output should be a buffer');
+
+    const randomDecompressed = zlib.zstdDecompressSync(randomCompressed);
+    assert(
+      randomInput.equals(randomDecompressed),
+      'Large random data round-trip should match'
+    );
   },
 };
 
diff --git a/src/workerd/api/node/zlib-util.c++ b/src/workerd/api/node/zlib-util.c++
index 26316394b00..ceac1efb901 100644
--- a/src/workerd/api/node/zlib-util.c++
+++ b/src/workerd/api/node/zlib-util.c++
@@ -902,11 +902,6 @@ kj::Maybe<CompressionError> ZstdEncoderContext::getError() const {
         kj::str("ERR_ZSTD_COMPRESSION_FAILED"), -1);
   }
 
-  if (flush_ == ZSTD_e_end && lastResult != 0) {
-    // lastResult > 0 means more output is needed, which shouldn't happen at end
-    return CompressionError("Unexpected end of file"_kj, "Z_BUF_ERROR"_kj, Z_BUF_ERROR);
-  }
-
   return kj::none;
 }
 
@@ -915,6 +910,10 @@ bool ZstdEncoderContext::isStreamEnd() const {
   return !ZSTD_isError(lastResult) && lastResult == 0;
 }
 
+bool ZstdEncoderContext::hasPendingOutput() const {
+  return flush_ == ZSTD_e_end && !ZSTD_isError(lastResult) && lastResult != 0;
+}
+
 ZstdDecoderContext::ZstdDecoderContext(ZlibMode _mode)
     : ZstdContext(_mode),
       dctx_(kj::disposeWith<zstdFreeDCtx>(ZSTD_createDCtx())) {}
@@ -1088,7 +1087,7 @@ static kj::Array<kj::byte> syncProcessBuffer(Context& ctx, GrowableBuffer& resul
       JSG_REQUIRE(ctx.isStreamEnd(), RangeError, "Memory limit exceeded");
       break;
     }
-  } while (ctx.getAvailOut() == 0);
+  } while (ctx.getAvailOut() == 0 || ctx.hasPendingInput() || ctx.hasPendingOutput());
 
   return result.releaseAsArray();
 }
diff --git a/src/workerd/api/node/zlib-util.h b/src/workerd/api/node/zlib-util.h
index 35121558a60..02275ebee7f 100644
--- a/src/workerd/api/node/zlib-util.h
+++ b/src/workerd/api/node/zlib-util.h
@@ -155,6 +155,14 @@ class ZlibContext final {
     return err == Z_STREAM_END;
   }
 
+  bool hasPendingOutput() const {
+    return false;
+  }
+
+  bool hasPendingInput() const {
+    return false;
+  }
+
   uint getAvailIn() const {
     return stream.avail_in;
   };
@@ -237,6 +245,9 @@ class BrotliContext {
   void setBuffers(kj::ArrayPtr<kj::byte> input, kj::ArrayPtr<kj::byte> output);
   void setInputBuffer(kj::ArrayPtr<const kj::byte> input);
   void setOutputBuffer(kj::ArrayPtr<kj::byte> output);
+  kj::uint getAvailIn() const {
+    return availIn;
+  }
   void setFlush(int flush);
   kj::uint getAvailOut() const;
   void getAfterWriteResult(uint32_t* availIn, uint32_t* availOut) const;
@@ -291,6 +302,12 @@ class BrotliEncoderContext final: public BrotliContext {
   kj::Maybe<CompressionError> setParams(int key, uint32_t value);
   kj::Maybe<CompressionError> getError() const;
   bool isStreamEnd() const;
+  bool hasPendingOutput() const {
+    return false;
+  }
+  bool hasPendingInput() const {
+    return false;
+  }
 
  private:
   bool lastResult = false;
@@ -313,6 +330,12 @@ class BrotliDecoderContext final: public BrotliContext {
   kj::Maybe<CompressionError> setParams(int key, uint32_t value);
   kj::Maybe<CompressionError> getError() const;
   bool isStreamEnd() const;
+  bool hasPendingOutput() const {
+    return false;
+  }
+  bool hasPendingInput() const {
+    return false;
+  }
 
  private:
   BrotliDecoderResult lastResult = BROTLI_DECODER_RESULT_SUCCESS;
@@ -329,6 +352,12 @@ class ZstdContext {
   void setBuffers(kj::ArrayPtr<kj::byte> input, kj::ArrayPtr<kj::byte> output);
   void setInputBuffer(kj::ArrayPtr<const kj::byte> input);
   void setOutputBuffer(kj::ArrayPtr<kj::byte> output);
+  kj::uint getAvailIn() const {
+    return input_.size - input_.pos;
+  }
+  bool hasPendingInput() const {
+    return false;
+  }
   void setFlush(int flush);
   kj::uint getAvailOut() const;
   void getAfterWriteResult(uint32_t* availIn, uint32_t* availOut) const;
@@ -370,6 +399,10 @@ class ZstdEncoderContext final: public ZstdContext {
   kj::Maybe<CompressionError> setParams(int key, int value);
   kj::Maybe<CompressionError> getError() const;
   bool isStreamEnd() const;
+  bool hasPendingOutput() const;
+  bool hasPendingInput() const {
+    return getAvailIn() != 0;
+  }
 
  private:
   size_t lastResult = 0;
@@ -389,6 +422,9 @@ class ZstdDecoderContext final: public ZstdContext {
   kj::Maybe<CompressionError> setParams(int key, int value);
   kj::Maybe<CompressionError> getError() const;
   bool isStreamEnd() const;
+  bool hasPendingOutput() const {
+    return false;
+  }
 
  private:
   size_t lastResult = 0;