diff --git a/data-prepper-api/src/main/java/org/opensearch/dataprepper/model/event/JacksonEventKey.java b/data-prepper-api/src/main/java/org/opensearch/dataprepper/model/event/JacksonEventKey.java
index 50d59a6585..fff70b1a6a 100644
--- a/data-prepper-api/src/main/java/org/opensearch/dataprepper/model/event/JacksonEventKey.java
+++ b/data-prepper-api/src/main/java/org/opensearch/dataprepper/model/event/JacksonEventKey.java
@@ -161,7 +161,8 @@ private static boolean isValidKey(final String key) {
                     || c == '@'
                     || c == '/'
                     || c == '['
-                    || c == ']')) {
+                    || c == ']'
+                    || c == '|')) {
 
                 return false;
             }
diff --git a/data-prepper-plugins/mutate-event-processors/src/main/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorConfig.java b/data-prepper-plugins/mutate-event-processors/src/main/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorConfig.java
index df7788e2d5..b3a08e837f 100644
--- a/data-prepper-plugins/mutate-event-processors/src/main/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorConfig.java
+++ b/data-prepper-plugins/mutate-event-processors/src/main/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorConfig.java
@@ -73,6 +73,9 @@ public String getRenameWhen() {
         }
 
         public Pattern getFromKeyCompiledPattern() {
+            if (fromKeyPattern != null && fromKeyCompiledPattern == null) {
+                fromKeyCompiledPattern = Pattern.compile(fromKeyPattern);
+            }
             return fromKeyCompiledPattern;
         }
 
@@ -82,9 +85,6 @@ public Entry(final EventKey fromKey, final String fromKeyPattern, final EventKey
             this.toKey = toKey;
             this.overwriteIfToKeyExists = overwriteIfKeyExists;
             this.renameWhen = renameWhen;
-            if (fromKeyPattern != null) {
-                fromKeyCompiledPattern = Pattern.compile(fromKeyPattern);
-            }
         }
 
         public Entry() {
diff --git a/data-prepper-plugins/mutate-event-processors/src/test/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorTests.java b/data-prepper-plugins/mutate-event-processors/src/test/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorTests.java
index b13b79d3e3..d9d0c67dc4 100644
--- a/data-prepper-plugins/mutate-event-processors/src/test/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorTests.java
+++ b/data-prepper-plugins/mutate-event-processors/src/test/java/org/opensearch/dataprepper/plugins/processor/mutateevent/RenameKeyProcessorTests.java
@@ -19,8 +19,15 @@
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 
-import java.util.*;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.UUID;
+import java.util.LinkedList;
+import java.util.Arrays;
+import java.util.Map;
 import java.util.ArrayList;
+import java.util.HashMap;
 
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.is;