diff --git a/adaptive_compress.c b/adaptive_compress.c
index 4714b0f..4f99be4 100644
--- a/adaptive_compress.c
+++ b/adaptive_compress.c
@@ -164,6 +164,7 @@ adapt2_init(void **data, int *level, int nthreads, uint64_t chunksize,
 		adat->ppmd_data = NULL;
 		adat->bsc_data = NULL;
 		lv = *level;
+		if (lv > 10) lv = 10;
 		rv = ppmd_init(&(adat->ppmd_data), &lv, nthreads, chunksize, file_version, op);
 		lv = *level;
 		if (rv == 0)
diff --git a/ppmd_compress.c b/ppmd_compress.c
index fafc362..609af42 100644
--- a/ppmd_compress.c
+++ b/ppmd_compress.c
@@ -30,6 +30,7 @@
 #include <pcompress.h>
 #include <allocator.h>
 #include <Ppmd8.h>
+#include <pthread.h>
 
 /*
  * PPMd model order to working set memory size mappings.
@@ -52,6 +53,9 @@ static unsigned int ppmd8_mem_sz[] = {
 	(1200 << 20)
 };
 
+static pthread_mutex_t mem_init_lock = PTHREAD_MUTEX_INITIALIZER;
+static int mem_inited = 0;
+
 static ISzAlloc g_Alloc = {
 	slab_alloc,
 	slab_free,
@@ -75,6 +79,13 @@ ppmd_init(void **data, int *level, int nthreads, uint64_t chunksize,
 {
 	CPpmd8 *_ppmd;
 
+	pthread_mutex_lock(&mem_init_lock);
+	if (!mem_inited) {
+		slab_cache_add(sizeof (CPpmd8));
+		slab_cache_add(ppmd8_mem_sz[*level]);
+		mem_inited = 1;
+	}
+	pthread_mutex_unlock(&mem_init_lock);
 	_ppmd = (CPpmd8 *)slab_alloc(NULL, sizeof (CPpmd8));
 	if (!_ppmd)
 		return (-1);