diff --git a/lib/libstand/sbrk.c b/lib/libstand/sbrk.c
index 93d94e482451..471e78ecf6df 100644
--- a/lib/libstand/sbrk.c
+++ b/lib/libstand/sbrk.c
@@ -33,6 +33,7 @@ __FBSDID("$FreeBSD$");
 
 #include <string.h>
 #include "stand.h"
+#include "zalloc_defs.h"
 
 static size_t	maxheap, heapsize = 0;
 static void	*heapbase;
@@ -40,8 +41,9 @@ static void	*heapbase;
 void
 setheap(void *base, void *top)
 {
-    /* Align start address to 16 bytes for the malloc code. Sigh. */
-    heapbase = (void *)(((uintptr_t)base + 15) & ~15);
+    /* Align start address for the malloc code.  Sigh. */
+    heapbase = (void *)(((uintptr_t)base + MALLOCALIGN_MASK) & 
+        ~MALLOCALIGN_MASK);
     maxheap = (char *)top - (char *)heapbase;
 }
 
diff --git a/lib/libstand/zalloc.c b/lib/libstand/zalloc.c
index 41aef0d30694..4d1ec6291210 100644
--- a/lib/libstand/zalloc.c
+++ b/lib/libstand/zalloc.c
@@ -70,6 +70,15 @@ __FBSDID("$FreeBSD$");
 
 #include "zalloc_defs.h"
 
+/*
+ * Objects in the pool must be aligned to at least the size of struct MemNode.
+ * They must also be aligned to MALLOCALIGN, which should normally be larger
+ * than the struct, so assert that to be so at compile time.
+ */
+typedef char assert_align[(sizeof(struct MemNode) <= MALLOCALIGN) ? 1 : -1];
+
+#define	MEMNODE_SIZE_MASK	MALLOCALIGN_MASK
+
 /*
  * znalloc() -	allocate memory (without zeroing) from pool.  Call reclaim
  *		and retry if appropriate, return NULL if unable to allocate
diff --git a/lib/libstand/zalloc_defs.h b/lib/libstand/zalloc_defs.h
index 5331ee068160..7f2cc1202c9b 100644
--- a/lib/libstand/zalloc_defs.h
+++ b/lib/libstand/zalloc_defs.h
@@ -52,18 +52,26 @@
 #define BLKEXTENDMASK	(BLKEXTEND - 1)
 
 /*
- * required malloc alignment.  Just hardwire to 16.
+ * Required malloc alignment.
  *
- * Note: if we implement a more sophisticated realloc, we should ensure that
- * MALLOCALIGN is at least as large as MemNode.
+ * Embedded platforms using the u-boot API drivers require that all I/O buffers
+ * be on a cache line sized boundary.  The worst case size for that is 64 bytes.
+ * For other platforms, 16 bytes works fine.  The alignment also must be at
+ * least sizeof(struct MemNode); this is asserted in zalloc.c.
  */
 
+#if defined(__arm__) || defined(__mips__) || defined(__powerpc__)
+#define	MALLOCALIGN		64
+#else
+#define	MALLOCALIGN		16
+#endif
+#define	MALLOCALIGN_MASK	(MALLOCALIGN - 1)
+
 typedef struct Guard {
     size_t	ga_Bytes;
     size_t	ga_Magic;	/* must be at least 32 bits */
 } Guard;
 
-#define MALLOCALIGN	16
 #define GAMAGIC		0x55FF44FD
 #define GAFREE		0x5F54F4DF
 
diff --git a/lib/libstand/zalloc_mem.h b/lib/libstand/zalloc_mem.h
index f29c0d7c0039..26d388dfc75e 100644
--- a/lib/libstand/zalloc_mem.h
+++ b/lib/libstand/zalloc_mem.h
@@ -48,8 +48,6 @@ typedef struct MemPool {
     uintptr_t		mp_Used;
 } MemPool;
 
-#define MEMNODE_SIZE_MASK       ((sizeof(MemNode) <= 8) ? 7 : 15)
-
 #define ZNOTE_FREE	0
 #define ZNOTE_REUSE	1