Index: module-nio/src/main/java/org/apache/http/impl/nio/reactor/SessionOutputBuffer.java =================================================================== --- module-nio/src/main/java/org/apache/http/impl/nio/reactor/SessionOutputBuffer.java (revision 544242) +++ module-nio/src/main/java/org/apache/http/impl/nio/reactor/SessionOutputBuffer.java (working copy) @@ -143,6 +143,9 @@ boolean retry = true; while (retry) { CoderResult result = this.charencoder.flush(this.buffer); + if (result.isError()) { + result.throwException(); + } if (result.isOverflow()) { expand(); }