diff --git a/picard.wdl b/picard.wdl
index 2a0121dc4d9d678d86414a6da609386c48bf7184..b78e60397da063549140fa94d42b6eece0d8538f 100644
--- a/picard.wdl
+++ b/picard.wdl
@@ -328,6 +328,7 @@ task CreateSequenceDictionary {
         set -e
         mkdir -p "$(dirname ~{outputDir})"
         picard -Xmx~{javaXmx} \
+        -XX:ParallelGCThreads=1 \
         CreateSequenceDictionary \
         REFERENCE=~{inputFile} \
         OUTPUT="~{outputDir}/~{basenameInputFile}.dict"