diff --git a/src/edu/csus/ecs/pc2/core/execute/Executable.java b/src/edu/csus/ecs/pc2/core/execute/Executable.java
index 8108d7e9a..630857363 100644
--- a/src/edu/csus/ecs/pc2/core/execute/Executable.java
+++ b/src/edu/csus/ecs/pc2/core/execute/Executable.java
@@ -1122,6 +1122,9 @@ protected boolean validateProgram(int dataSetNumber) {
 
 
             executionData.setvalidateTimeMS(System.currentTimeMillis() - startTime);
+            // be sure to flush before serializing.
+            stdoutlog.flush();
+            stderrlog.flush();
             executionData.setValidationStdout(new SerializedFile(prefixExecuteDirname(VALIDATOR_STDOUT_FILENAME)));
             executionData.setValidationStderr(new SerializedFile(prefixExecuteDirname(VALIDATOR_STDERR_FILENAME)));