diff --git a/plugins/nf-quilt/src/main/nextflow/quilt/jep/QuiltPackage.groovy b/plugins/nf-quilt/src/main/nextflow/quilt/jep/QuiltPackage.groovy
index 4db85cb5..1c19f6c8 100644
--- a/plugins/nf-quilt/src/main/nextflow/quilt/jep/QuiltPackage.groovy
+++ b/plugins/nf-quilt/src/main/nextflow/quilt/jep/QuiltPackage.groovy
@@ -39,12 +39,15 @@ import com.quiltdata.quiltcore.key.LocalPhysicalKey
 import com.quiltdata.quiltcore.key.S3PhysicalKey
 
 import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.databind.ObjectWriter
 import com.fasterxml.jackson.databind.node.ObjectNode
 
 @Slf4j
 @CompileStatic
 class QuiltPackage {
 
+    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
+    private static final ObjectWriter OBJECT_WRITER = OBJECT_MAPPER.writerWithDefaultPrettyPrinter()
     private static final Map<String,QuiltPackage> PKGS = [:]
     private static final String INSTALL_PREFIX = 'QuiltPackage'
     static final Path INSTALL_ROOT = Files.createTempDirectory(INSTALL_PREFIX)
@@ -83,11 +86,11 @@ class QuiltPackage {
 
     static String toJson(Map dict) {
         List<String> entries = dict.collect { key, value ->
-            String prefix = JsonOutput.toJson(key)
+            String prefix = OBJECT_WRITER.writeValueAsString(key)
             log.debug("toJson.${key}: ${value}")
             String suffix = "toJson.error[${value}]"
             try {
-                suffix = JsonOutput.toJson(value)
+                suffix = OBJECT_WRITER.writeValueAsString(value)
             }
             catch (Exception e) {
                 log.error(suffix, e)