diff --git a/primeseq/src/org/labkey/primeseq/PrimeseqController.java b/primeseq/src/org/labkey/primeseq/PrimeseqController.java
index bcd58996..cac4973a 100644
--- a/primeseq/src/org/labkey/primeseq/PrimeseqController.java
+++ b/primeseq/src/org/labkey/primeseq/PrimeseqController.java
@@ -556,7 +556,7 @@ else if (!sf.lookupContainer().hasPermission(getUser(), ReadPermission.class))
                         json.put(prop, paramJson.get(prop));
                     }
 
-                    try (PrintWriter writer = PrintWriters.getPrintWriter(sj.getParametersFile()))
+                    try (PrintWriter writer = PrintWriters.getPrintWriter(sj.getParametersFile().openOutputStream()))
                     {
                         writer.write(json.toString(1));
                     }