diff --git a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ThreadLocalAllocation.java b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ThreadLocalAllocation.java
index 9535f996f5b04..a1c44fce4de3a 100644
--- a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ThreadLocalAllocation.java
+++ b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ThreadLocalAllocation.java
@@ -323,11 +323,17 @@ private static Object slowPathNewArrayLikeObjectWithoutAllocation0(DynamicHub hu
         Object array;
         if (!GenScavengeAllocationSupport.shouldAllocateInAlignedChunk(size)) {
             /*
-             * Large arrays go into their own unaligned chunk. Only arrays and stored continuations
-             * may be allocated in an unaligned chunk.
+             * Large arrays go into their own unaligned chunk.
+             *
+             * Instance objects with object reference fields, including hybrid objects such as pods,
+             * must not be allocated in unaligned chunks because field write barriers assume an
+             * aligned chunk.
              */
             int layoutEncoding = hub.getLayoutEncoding();
-            assert LayoutEncoding.isArray(layoutEncoding) || StoredContinuation.class.isAssignableFrom(DynamicHub.toClass(hub));
+            if (!LayoutEncoding.isArray(layoutEncoding) && !StoredContinuation.class.isAssignableFrom(DynamicHub.toClass(hub))) {
+                throw VMError.shouldNotReachHere("Only arrays and StoredContinuation may be allocated in an unaligned chunk. " +
+                                "Hybrid objects such as pods must be small enough to be allocated in an aligned chunk.");
+            }
 
             boolean needsZeroing = !HeapChunkProvider.areUnalignedChunksZeroed();
             UnalignedHeapChunk.UnalignedHeader newTlabChunk = HeapImpl.getChunkProvider().produceUnalignedChunk(size);
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/StoredContinuation.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/StoredContinuation.java
index 2b9761c60e71e..a904321bcc313 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/StoredContinuation.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/StoredContinuation.java
@@ -36,7 +36,12 @@
  *
  * Stored continuations are {@link Hybrid} objects where the array part contains the raw stack data.
  * After writing the stack data into the object, we manually emit the correct GC write barriers for
- * all the references (see {@link Heap#dirtyAllReferencesOf}).
+ * all the references (see {@link Heap#dirtyAllReferencesOf}). Following initialization, an object
+ * is considered effectively immutable, and only GC is expected to write the references it contains.
+ * Therefore, implicit write barriers intentionally do not support stored continuations, and they
+ * cannot have declared object reference fields.
+ *
+ * Objects of this type can reside in unaligned chunks.
  */
 @Hybrid(componentType = Word.class)
 public final class StoredContinuation {