diff -Naur umem-1.0/umem_impl.h umem-1.0.p1/umem_impl.h
--- umem-1.0/umem_impl.h	2006-03-10 02:45:59.000000000 +0000
+++ umem-1.0.p1/umem_impl.h	2008-06-02 09:32:40.000000000 +0000
@@ -235,11 +235,12 @@
 	umem_cache_t	*mt_cache;	/* magazine cache */
 } umem_magtype_t;
 
-#if (defined(__PTHREAD_MUTEX_SIZE__) && __PTHREAD_MUTEX_SIZE__ >= 24) || defined(UMEM_PTHREAD_MUTEX_TOO_BIG)
+#if (defined(__PTHREAD_MUTEX_SIZE__) && __PTHREAD_MUTEX_SIZE__ >= 24) || defined(UMEM_PTHREAD_MUTEX_TOO_BIG) || defined(_LP64)
 #define	UMEM_CPU_CACHE_SIZE	128	/* must be power of 2 */
 #else
 #define	UMEM_CPU_CACHE_SIZE	64	/* must be power of 2 */
 #endif
+
 #define	UMEM_CPU_PAD		(UMEM_CPU_CACHE_SIZE - sizeof (mutex_t) - \
 	2 * sizeof (uint_t) - 2 * sizeof (void *) - 4 * sizeof (int))
 #define	UMEM_CACHE_SIZE(ncpus)	\
@@ -255,7 +256,7 @@
 	int		cc_prounds;	/* number of objects in previous mag */
 	int		cc_magsize;	/* number of rounds in a full mag */
 	int		cc_flags;	/* CPU-local copy of cache_flags */
-#if (!defined(_LP64) || defined(UMEM_PTHREAD_MUTEX_TOO_BIG)) && !defined(_WIN32)
+#if !defined(_WIN32)
 	/* on win32, UMEM_CPU_PAD evaluates to zero, and the MS compiler
 	 * won't allow static initialization of arrays containing structures
 	 * that contain zero size arrays */