diff -r baf88aa4f5db -r 0ef79bd7fb5c src/jdk.jfr/share/classes/jdk/jfr/internal/RequestEngine.java
--- a/src/jdk.jfr/share/classes/jdk/jfr/internal/RequestEngine.java	Tue Sep 17 19:37:49 2019 +0200
+++ b/src/jdk.jfr/share/classes/jdk/jfr/internal/RequestEngine.java	Wed Sep 18 03:45:46 2019 +0200
@@ -279,7 +279,9 @@
         return min;
     }
 
-    public static void setFlushInterval(long interval) {
+    static void setFlushInterval(long millis) {
+        // Don't accept shorter interval than 1 s.
+        long interval = millis < 1000 ? 1000  : millis;
         flushInterval = interval;
         if (interval < flushInterval) {
             synchronized (JVM.FILE_DELTA_CHANGE) {