diff --git a/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingField.java b/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingField.java
index 8e5e979..967b2f6 100644
--- a/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingField.java
+++ b/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingField.java
@@ -4,7 +4,7 @@
  * @author <a href="mailto:krzysztof.suszynski@coi.gov.pl">Krzysztof Suszynski</a>
  * @since 27.04.18
  */
-public interface InspectingField {
+interface InspectingField {
   boolean shouldInspect();
   boolean showNull();
 }
diff --git a/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingFieldFactory.java b/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingFieldFactory.java
index 9f1e6fe..e9e8123 100644
--- a/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingFieldFactory.java
+++ b/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingFieldFactory.java
@@ -2,7 +2,6 @@
 
 import lombok.RequiredArgsConstructor;
 import pl.wavesoftware.utils.stringify.configuration.BeanFactory;
-import pl.wavesoftware.utils.stringify.configuration.DisplayNull;
 import pl.wavesoftware.utils.stringify.configuration.InspectionPoint;
 import pl.wavesoftware.utils.stringify.configuration.Mode;
 
@@ -27,30 +26,4 @@ private InspectFieldPredicate createPredicate(BeanFactory beanFactory) {
     }
   }
 
-  @RequiredArgsConstructor
-  private class InspectingFieldImpl implements InspectingField {
-    private final InspectionPoint inspectionPoint;
-    private final InspectFieldPredicate predicate;
-
-    @Override
-    public boolean shouldInspect() {
-      return technically() && predicate.shouldInspect(inspectionPoint);
-    }
-
-    private boolean technically() {
-      return !inspectionPoint.getField().isEnumConstant()
-        && !inspectionPoint.getField().isSynthetic();
-    }
-
-    @Override
-    public boolean showNull() {
-      DisplayNull displayNull = inspectionPoint.getField()
-        .getAnnotation(DisplayNull.class);
-      if (displayNull != null) {
-        return displayNull.value();
-      } else {
-        return DisplayNull.BY_DEFAULT;
-      }
-    }
-  }
 }
diff --git a/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingFieldImpl.java b/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingFieldImpl.java
new file mode 100644
index 0000000..2fe1b29
--- /dev/null
+++ b/src/main/java/pl/wavesoftware/utils/stringify/impl/InspectingFieldImpl.java
@@ -0,0 +1,42 @@
+package pl.wavesoftware.utils.stringify.impl;
+
+import lombok.RequiredArgsConstructor;
+import pl.wavesoftware.utils.stringify.configuration.DisplayNull;
+import pl.wavesoftware.utils.stringify.configuration.InspectionPoint;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+
+/**
+ * @author <a href="krzysztof.suszynski@wavesoftware.pl">Krzysztof Suszyński</a>
+ * @since 2018-04-30
+ */
+@RequiredArgsConstructor
+final class InspectingFieldImpl implements InspectingField {
+  private final InspectionPoint inspectionPoint;
+  private final InspectFieldPredicate predicate;
+
+  @Override
+  public boolean shouldInspect() {
+    return technically() && predicate.shouldInspect(inspectionPoint);
+  }
+
+  private boolean technically() {
+    Field field = inspectionPoint.getField();
+    int mods = field.getModifiers();
+    return !Modifier.isStatic(mods)
+      && !field.isEnumConstant()
+      && !field.isSynthetic();
+  }
+
+  @Override
+  public boolean showNull() {
+    DisplayNull displayNull = inspectionPoint.getField()
+      .getAnnotation(DisplayNull.class);
+    if (displayNull != null) {
+      return displayNull.value();
+    } else {
+      return DisplayNull.BY_DEFAULT;
+    }
+  }
+}
diff --git a/src/test/java/pl/wavesoftware/utils/stringify/Earth.java b/src/test/java/pl/wavesoftware/utils/stringify/Earth.java
index 71b80cd..0fd433c 100644
--- a/src/test/java/pl/wavesoftware/utils/stringify/Earth.java
+++ b/src/test/java/pl/wavesoftware/utils/stringify/Earth.java
@@ -11,6 +11,9 @@
 @Data
 @EqualsAndHashCode(callSuper = true)
 final class Earth extends Planet {
+
+  private static final long serialVersionUID = 20180430201544L;
+
   @Inspect
   private Moon moon;
   @Inspect
diff --git a/src/test/java/pl/wavesoftware/utils/stringify/Moon.java b/src/test/java/pl/wavesoftware/utils/stringify/Moon.java
index fcb4e19..d335b60 100644
--- a/src/test/java/pl/wavesoftware/utils/stringify/Moon.java
+++ b/src/test/java/pl/wavesoftware/utils/stringify/Moon.java
@@ -17,6 +17,9 @@
 @ToString(exclude = "nullinside")
 @EqualsAndHashCode(callSuper = true)
 final class Moon extends Planet {
+
+  private static final long serialVersionUID = 20180430201602L;
+
   @Inspect
   private Phase phase;
   @Inspect
diff --git a/src/test/java/pl/wavesoftware/utils/stringify/Person.java b/src/test/java/pl/wavesoftware/utils/stringify/Person.java
index cdb6a67..775be3b 100644
--- a/src/test/java/pl/wavesoftware/utils/stringify/Person.java
+++ b/src/test/java/pl/wavesoftware/utils/stringify/Person.java
@@ -13,9 +13,9 @@
  */
 @Setter
 class Person {
-  private int id;
+  private volatile int id;
   @DisplayNull
-  private Person parent;
+  private transient Person parent;
   private List<Person> childs;
   private Account account;
   @Inspect(conditionally = IsInDevelopment.class)
diff --git a/src/test/java/pl/wavesoftware/utils/stringify/Planet.java b/src/test/java/pl/wavesoftware/utils/stringify/Planet.java
index efe21c0..4fc999f 100644
--- a/src/test/java/pl/wavesoftware/utils/stringify/Planet.java
+++ b/src/test/java/pl/wavesoftware/utils/stringify/Planet.java
@@ -5,12 +5,17 @@
 import pl.wavesoftware.utils.stringify.configuration.DoNotInspect;
 import pl.wavesoftware.utils.stringify.configuration.Inspect;
 
+import java.io.Serializable;
+
 /**
  * @author <a href="krzysztof.suszynski@wavesoftware.pl">Krzysztof Suszyński</a>
  * @since 2018-04-18
  */
 @Data
-abstract class Planet {
+abstract class Planet implements Serializable {
+
+  private static final long serialVersionUID = 20180430201529L;
+
   @Inspect
   private String name;
   @Inspect