diff --git a/logstash-core/src/main/java/org/logstash/Accessors.java b/logstash-core/src/main/java/org/logstash/Accessors.java
index 705f3b216..ec65795c3 100644
--- a/logstash-core/src/main/java/org/logstash/Accessors.java
+++ b/logstash-core/src/main/java/org/logstash/Accessors.java
@@ -33,11 +33,11 @@ public class Accessors {
             if (target instanceof Map) {
                 return ((Map<String, Object>) target).remove(field.getKey());
             } else if (target instanceof List) {
-                int i = Integer.parseInt(field.getKey());
                 try {
+                    int i = Integer.parseInt(field.getKey());
                     int offset = listIndex(i, ((List) target).size());
                     return ((List)target).remove(offset);
-                } catch (IndexOutOfBoundsException e) {
+                } catch (IndexOutOfBoundsException|NumberFormatException e) {
                     return null;
                 }
             } else {
@@ -52,8 +52,13 @@ public class Accessors {
         Object target = findTarget(field);
         if (target instanceof Map && foundInMap((Map<String, Object>) target, field.getKey())) {
             return true;
-        } else if (target instanceof List && foundInList((List<Object>) target, Integer.parseInt(field.getKey()))) {
-            return true;
+        } else if (target instanceof List) {
+            try {
+                int i = Integer.parseInt(field.getKey());
+                return (foundInList((List<Object>) target, i) ? true : false);
+            } catch (NumberFormatException e) {
+                return false;
+            }
         } else {
             return false;
         }
@@ -98,9 +103,13 @@ public class Accessors {
                 if (target instanceof Map) {
                     ((Map<String, Object>)target).put(key, result);
                 } else if (target instanceof List) {
-                    int i = Integer.parseInt(key);
-                    // TODO: what about index out of bound?
-                    ((List<Object>)target).set(i, result);
+                    try {
+                        int i = Integer.parseInt(key);
+                        // TODO: what about index out of bound?
+                        ((List<Object>)target).set(i, result);
+                    } catch (NumberFormatException e) {
+                        continue;
+                    }
                 } else if (target != null) {
                     throw newCollectionException(target);
                 }
@@ -135,7 +144,7 @@ public class Accessors {
             try {
                 int offset = listIndex(Integer.parseInt(key), ((List) target).size());
                 return ((List<Object>) target).get(offset);
-            } catch (IndexOutOfBoundsException e) {
+            } catch (IndexOutOfBoundsException|NumberFormatException e) {
                 return null;
             }
         } else if (target == null) {
@@ -149,7 +158,12 @@ public class Accessors {
         if (target instanceof Map) {
             ((Map<String, Object>) target).put(key, value);
         } else if (target instanceof List) {
-            int i = Integer.parseInt(key);
+            int i;
+            try {
+                i = Integer.parseInt(key);
+            } catch (NumberFormatException e) {
+                return null;
+            }
             int size = ((List<Object>) target).size();
             if (i >= size) {
                 // grow array by adding trailing null items
diff --git a/logstash-core/src/test/java/org/logstash/AccessorsTest.java b/logstash-core/src/test/java/org/logstash/AccessorsTest.java
index 634ef9ad8..3218e96c5 100644
--- a/logstash-core/src/test/java/org/logstash/AccessorsTest.java
+++ b/logstash-core/src/test/java/org/logstash/AccessorsTest.java
@@ -127,6 +127,30 @@ public class AccessorsTest {
         assertEquals(accessors.get(reference), null);
         assertEquals(accessors.lutGet(reference), inner);
     }
+    /*
+     * Check if accessors are able to recovery from
+     * failure to convert the key (string) to integer,
+     * when it is a non-numeric value, which is not
+     * expected.
+     */
+    @Test
+    public void testInvalidIdList() throws Exception {
+        Map data = new HashMap();
+        List inner = new ArrayList();
+        data.put("map1", inner);
+        inner.add("obj1");
+        inner.add("obj2");
+
+        String reference = "[map1][IdNonNumeric]";
+
+        TestableAccessors accessors = new TestableAccessors(data);
+        assertEquals(accessors.lutGet(reference), null);
+        assertEquals(accessors.get(reference), null);
+        assertEquals(accessors.set(reference, "obj3"), null);
+        assertEquals(accessors.lutGet(reference), inner);
+        assertFalse(accessors.includes(reference));
+        assertEquals(accessors.del(reference), null);
+    }
 
     @Test
     public void testBarePut() throws Exception {