diff --git a/build.gradle b/build.gradle
index 124e943..4e5798b 100644
--- a/build.gradle
+++ b/build.gradle
@@ -52,7 +52,7 @@ dependencies {
     }
     compile('org.embulk:embulk-util-retryhelper-jetty92:0.8.2')
     compile 'org.embulk:embulk-util-timestamp:0.2.1'
-    compile('org.embulk:embulk-util-guess:0.1.2')
+    compile('org.embulk:embulk-util-guess:0.2.0')
 
     compile('org.embulk:embulk-util-json:0.1.1') {
         exclude group: 'com.fasterxml.jackson.core', module: 'jackson-core'
diff --git a/gradle/dependency-locks/embulkPluginRuntime.lockfile b/gradle/dependency-locks/embulkPluginRuntime.lockfile
index b9b65dd..dea1036 100644
--- a/gradle/dependency-locks/embulkPluginRuntime.lockfile
+++ b/gradle/dependency-locks/embulkPluginRuntime.lockfile
@@ -25,13 +25,13 @@ org.eclipse.jetty:jetty-http:9.2.14.v20151106
 org.eclipse.jetty:jetty-io:9.2.14.v20151106
 org.eclipse.jetty:jetty-util:9.2.14.v20151106
 org.embulk:embulk-util-config:0.3.1
-org.embulk:embulk-util-file:0.1.1
-org.embulk:embulk-util-guess:0.1.2
+org.embulk:embulk-util-file:0.1.3
+org.embulk:embulk-util-guess:0.2.0
 org.embulk:embulk-util-json:0.1.1
 org.embulk:embulk-util-retryhelper-jetty92:0.8.2
 org.embulk:embulk-util-retryhelper:0.8.2
 org.embulk:embulk-util-rubytime:0.3.2
-org.embulk:embulk-util-text:0.1.0
+org.embulk:embulk-util-text:0.1.1
 org.embulk:embulk-util-timestamp:0.2.1
 org.glassfish.hk2.external:javax.inject:2.5.0-b42
 org.glassfish.hk2:osgi-resource-locator:1.0.1
diff --git a/src/main/java/org/embulk/input/jira/util/JiraUtil.java b/src/main/java/org/embulk/input/jira/util/JiraUtil.java
index f3ab47a..59df1dc 100644
--- a/src/main/java/org/embulk/input/jira/util/JiraUtil.java
+++ b/src/main/java/org/embulk/input/jira/util/JiraUtil.java
@@ -273,6 +273,9 @@ public static LinkedHashMap<String, Object> toLinkedHashMap(final JsonObject flt
             if (elem.isJsonPrimitive()) {
                 result.put(key, flt.get(key).getAsString());
             }
+            else if(elem.isJsonNull()) {
+                result.put(key, null);
+            }
             else {
                 result.put(key, elem);
             }