diff --git a/httpclient5/src/main/java/org/apache/hc/client5/http/utils/ByteArrayBuilder.java b/httpclient5/src/main/java/org/apache/hc/client5/http/utils/ByteArrayBuilder.java
index 6b78abcb2..f68797ac5 100644
--- a/httpclient5/src/main/java/org/apache/hc/client5/http/utils/ByteArrayBuilder.java
+++ b/httpclient5/src/main/java/org/apache/hc/client5/http/utils/ByteArrayBuilder.java
@@ -74,8 +74,8 @@ public final class ByteArrayBuilder {
 
         final int capacity = (int) (in.remaining() * encoder.averageBytesPerChar());
         ByteBuffer out = ensureFreeCapacity(buffer, capacity);
-        for (;;) {
-            CoderResult result = in.hasRemaining() ? encoder.encode(in, out, true) : CoderResult.UNDERFLOW;
+        while (in.hasRemaining()) {
+            CoderResult result = encoder.encode(in, out, true);
             if (result.isError()) {
                 result.throwException();
             }
diff --git a/httpclient5/src/test/java/org/apache/hc/client5/http/utils/TestByteArrayBuilder.java b/httpclient5/src/test/java/org/apache/hc/client5/http/utils/TestByteArrayBuilder.java
index 785afb21d..d43709fb9 100644
--- a/httpclient5/src/test/java/org/apache/hc/client5/http/utils/TestByteArrayBuilder.java
+++ b/httpclient5/src/test/java/org/apache/hc/client5/http/utils/TestByteArrayBuilder.java
@@ -96,6 +96,7 @@ public class TestByteArrayBuilder {
         buffer.append("bcd");
         buffer.append("e");
         buffer.append("f");
+        buffer.append("");
         buffer.append((String) null);
         buffer.append((char[]) null);