diff --git a/env/posix/ocf_env.h b/env/posix/ocf_env.h
index d255174..c175c31 100644
--- a/env/posix/ocf_env.h
+++ b/env/posix/ocf_env.h
@@ -71,6 +71,8 @@ typedef uint64_t sector_t;
 
 #define ENV_BUG()			assert(0)
 #define ENV_BUG_ON(cond)		do { if (cond) ENV_BUG(); } while (0)
+#define ENV_BUILD_BUG_ON(cond)		_Static_assert(!(cond), "static "\
+					"assertion failure")
 
 /* MISC UTILITIES */
 #define container_of(ptr, type, member) ({          \
diff --git a/inc/ocf_def.h b/inc/ocf_def.h
index b5a4364..bdbe211 100644
--- a/inc/ocf_def.h
+++ b/inc/ocf_def.h
@@ -352,6 +352,6 @@ typedef enum {
  * @}
  */
 
-#define MAX_TRIM_RQ_SIZE	(1 * MiB)
+#define MAX_TRIM_RQ_SIZE	(512 * KiB)
 
 #endif /* __OCF_DEF_H__ */
diff --git a/src/ocf_request.c b/src/ocf_request.c
index 8584b71..d15ca01 100644
--- a/src/ocf_request.c
+++ b/src/ocf_request.c
@@ -42,7 +42,7 @@ struct ocf_req_allocator {
 
 static inline size_t ocf_req_sizeof_map(struct ocf_request *req)
 {
-	uint32_t lines = req->alloc_core_line_count;
+	uint32_t lines = req->core_line_count;
 	size_t size = (lines * sizeof(struct ocf_map_info));
 
 	ENV_BUG_ON(lines == 0);
@@ -224,6 +224,9 @@ int ocf_req_alloc_map(struct ocf_request *req)
 
 int ocf_req_alloc_map_discard(struct ocf_request *req)
 {
+	ENV_BUILD_BUG_ON(MAX_TRIM_RQ_SIZE / ocf_cache_line_size_4 *
+			sizeof(struct ocf_map_info) > 4 * KiB);
+
 	if (req->byte_length <= MAX_TRIM_RQ_SIZE)
 		return ocf_req_alloc_map(req);