diff --git a/base/src/main/groovy/org/asciidoctor/gradle/base/AbstractImplementationEngineExtension.groovy b/base/src/main/groovy/org/asciidoctor/gradle/base/AbstractImplementationEngineExtension.groovy
index 00761fcb8..7c53cfe94 100644
--- a/base/src/main/groovy/org/asciidoctor/gradle/base/AbstractImplementationEngineExtension.groovy
+++ b/base/src/main/groovy/org/asciidoctor/gradle/base/AbstractImplementationEngineExtension.groovy
@@ -295,7 +295,7 @@ class AbstractImplementationEngineExtension
     protected Collection<String> stringizeList(
             Collection<Object> list,
             boolean fromTaskOnly,
-            Function<AbstractImplementationEngineExtension,Collection<String>> other
+            Function<AbstractImplementationEngineExtension, Collection<String>> other
     ) {
         if (!task || fromTaskOnly) {
             stringize(list)
@@ -325,7 +325,7 @@ class AbstractImplementationEngineExtension
                 case Callable:
                     return item
                 default:
-                    return { -> projectOperations.stringTools.stringize(item) } as Callable<String>
+                    return { -> projectOperations.stringTools.stringizeOrNull(item) } as Callable<String>
             }
         }
     }
@@ -346,7 +346,7 @@ class AbstractImplementationEngineExtension
                 case Callable:
                     return [key, item]
                 default:
-                    return [key, { -> projectOperations.stringTools.stringize(item) } as Callable<String>]
+                    return [key, { -> projectOperations.stringTools.stringizeOrNull(item) } as Callable<String>]
             }
         } as Map<String, Object>
     }
@@ -356,6 +356,6 @@ class AbstractImplementationEngineExtension
     }
 
     private List<String> stringize(Collection<?> stringyThings) {
-        projectOperations.stringTools.stringize(stringyThings)
+        projectOperations.stringTools.stringizeDropNull(stringyThings)
     }
 }
diff --git a/gradle.properties b/gradle.properties
index 3d7cd2cb4..1a252dba0 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -10,7 +10,7 @@ project_vcs         = https://github.com/asciidoctor/asciidoctor-gradle-plugin.g
 cglibVersion           = 3.3.0
 jsoupVersion           = 1.17.2
 spockVersion           = 2.3-groovy-3.0
-grolifantVersion       = 2.2.3
+grolifantVersion       = 3.0.0
 jacocoVersion          = 0.8.6
 codenarcVersion        = 3.3.0
 nodejsGradleVersion    = 2.2.0
diff --git a/js/src/main/groovy/org/asciidoctor/gradle/js/nodejs/internal/AsciidoctorJSRunner.groovy b/js/src/main/groovy/org/asciidoctor/gradle/js/nodejs/internal/AsciidoctorJSRunner.groovy
index c83ba1881..81d2b476f 100644
--- a/js/src/main/groovy/org/asciidoctor/gradle/js/nodejs/internal/AsciidoctorJSRunner.groovy
+++ b/js/src/main/groovy/org/asciidoctor/gradle/js/nodejs/internal/AsciidoctorJSRunner.groovy
@@ -78,9 +78,14 @@ class AsciidoctorJSRunner {
             arguments.addAll([DOCTYPE, doctype.get()])
         }
 
-        arguments.addAll(attributes.collectMany { String key, String value ->
-            value ? [ATTR, "${key}=${value}".toString()] : [ATTR, key]
-        })
+        attributes.each { String key, String value ->
+            arguments.addAll(value ? [ATTR, "${key}=${value}".toString()] : [ATTR, key])
+        }
+        // Cannot use the better form of code as below, due to some Groovy incompatibility
+        // Therefore using the above code
+        //        arguments.addAll(attributes.collectMany { String key, String value ->
+        //            value ? [ATTR, "${key}=${value}".toString()] : [ATTR, key]
+        //        })
 
         arguments.addAll(requires.collectMany {
             [REQUIRE, it]