Index: compile.c
===================================================================
--- compile.c	(revision 48073)
+++ compile.c	(working copy)
@@ -590,6 +590,15 @@
     struct iseq_compile_data_storage *storage =
 	iseq->compile_data->storage_current;
 
+    size_t mod = 0;
+
+    /* The code assumes that SIZEOF_VALUE is 2 ** N,
+     * SIZEOF_VALUE is enough for word-alignment, and
+     * &storage->buff[0] is always word-aligned. */
+    if ((mod = size & (size_t)(SIZEOF_VALUE - 1)) > 0) {
+      size += (SIZEOF_VALUE - mod);
+    }
+
     if (storage->pos + size > storage->size) {
 	unsigned long alloc_size = storage->size * 2;