diff --git a/CHANGELOG.md b/CHANGELOG.md
index dee395cbc8962..724a75e4e0405 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -79,6 +79,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Replaces ZipInputStream with ZipFile to fix Zip Slip vulnerability ([#7230](https://github.com/opensearch-project/OpenSearch/pull/7230))
 - Add missing validation/parsing of SearchBackpressureMode of SearchBackpressureSettings ([#7541](https://github.com/opensearch-project/OpenSearch/pull/7541))
 - Adds log4j configuration for telemetry LogSpanExporter ([#8393](https://github.com/opensearch-project/OpenSearch/pull/8393))
+- Fix painless casting bug, which crashes the OpenSearch process ([#8315](https://github.com/opensearch-project/OpenSearch/pull/8315))
 
 ### Security
 
diff --git a/modules/lang-painless/src/main/java/org/opensearch/painless/AnalyzerCaster.java b/modules/lang-painless/src/main/java/org/opensearch/painless/AnalyzerCaster.java
index e375ff14db67e..d830ef2ab6290 100644
--- a/modules/lang-painless/src/main/java/org/opensearch/painless/AnalyzerCaster.java
+++ b/modules/lang-painless/src/main/java/org/opensearch/painless/AnalyzerCaster.java
@@ -412,7 +412,7 @@ public static PainlessCast getLegalCast(Location location, Class<?> actual, Clas
             }
         }
 
-        if (actual == def.class
+        if ((actual == def.class && expected != void.class)
             || (actual != void.class && expected == def.class)
             || expected.isAssignableFrom(actual)
             || (actual.isAssignableFrom(expected) && explicit)) {
diff --git a/modules/lang-painless/src/test/java/org/opensearch/painless/FactoryTests.java b/modules/lang-painless/src/test/java/org/opensearch/painless/FactoryTests.java
index 95b18cf1c5250..b4e322e12bc45 100644
--- a/modules/lang-painless/src/test/java/org/opensearch/painless/FactoryTests.java
+++ b/modules/lang-painless/src/test/java/org/opensearch/painless/FactoryTests.java
@@ -360,6 +360,14 @@ public void testVoidReturn() {
         assertEquals(iae.getMessage(), "not a statement: result not used from addition operation [+]");
     }
 
+    public void testDefToVoidReturnThrowsException() {
+        ClassCastException exception = expectScriptThrows(
+            ClassCastException.class,
+            () -> getEngine().compile("def_return_in_void", "def x=1;return x;", VoidReturnTestScript.CONTEXT, Collections.emptyMap())
+        );
+        assertEquals(exception.getMessage(), "Cannot cast from [def] to [void].");
+    }
+
     public abstract static class FactoryTestConverterScript {
         private final Map<String, Object> params;