diff --git a/lfs.c b/lfs.c
index b21d209..b7cc675 100644
--- a/lfs.c
+++ b/lfs.c
@@ -278,7 +278,7 @@ static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
                 % (lfs_soff_t)(lfs->cfg->block_count))
             + lfs->cfg->block_count) % lfs->cfg->block_count;
 
-    if (off < lfs->cfg->lookahead) {
+    if (off < lfs->free.size) {
         lfs->free.buffer[off / 32] |= 1U << (off % 32);
     }
 
@@ -287,18 +287,7 @@ static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
 
 static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
     while (true) {
-        while (true) {
-            // check if we have looked at all blocks since last ack
-            if (lfs->free.begin + lfs->free.off == lfs->free.end) {
-                LFS_WARN("No more free space %d", lfs->free.end);
-                return LFS_ERR_NOSPC;
-            }
-
-            if (lfs->free.off >= lfs_min(
-                    lfs->cfg->lookahead, lfs->cfg->block_count)) {
-                break;
-            }
-
+        while (lfs->free.off != lfs->free.size) {
             lfs_block_t off = lfs->free.off;
             lfs->free.off += 1;
 
@@ -309,7 +298,15 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
             }
         }
 
-        lfs->free.begin += lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count);
+        // check if we have looked at all blocks since last ack
+        if (lfs->free.off == lfs->free.ack - lfs->free.begin) {
+            LFS_WARN("No more free space %d", lfs->free.off + lfs->free.begin);
+            return LFS_ERR_NOSPC;
+        }
+
+        lfs->free.begin += lfs->free.size;
+        lfs->free.size = lfs_min(lfs->cfg->lookahead,
+                lfs->free.ack - lfs->free.begin);
         lfs->free.off = 0;
 
         // find mask of free blocks from tree
@@ -322,7 +319,7 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
 }
 
 static void lfs_alloc_ack(lfs_t *lfs) {
-    lfs->free.end = lfs->free.begin + lfs->free.off + lfs->cfg->block_count;
+    lfs->free.ack = lfs->free.off-1 + lfs->free.begin + lfs->cfg->block_count;
 }
 
 
@@ -2035,11 +2032,11 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
     // create free lookahead
     memset(lfs->free.buffer, 0, lfs->cfg->lookahead/8);
     lfs->free.begin = 0;
+    lfs->free.size = lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count);
     lfs->free.off = 0;
-    lfs->free.end = lfs->free.begin + lfs->free.off + lfs->cfg->block_count;
+    lfs_alloc_ack(lfs);
 
     // create superblock dir
-    lfs_alloc_ack(lfs);
     lfs_dir_t superdir;
     err = lfs_dir_alloc(lfs, &superdir);
     if (err) {
@@ -2112,9 +2109,10 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
     }
 
     // setup free lookahead
-    lfs->free.begin = -lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count);
-    lfs->free.off = -lfs->free.begin;
-    lfs->free.end = lfs->free.begin + lfs->free.off + lfs->cfg->block_count;
+    lfs->free.begin = 0;
+    lfs->free.size = 0;
+    lfs->free.off = 0;
+    lfs_alloc_ack(lfs);
 
     // load superblock
     lfs_dir_t dir;
diff --git a/lfs.h b/lfs.h
index 4ce8878..e24c308 100644
--- a/lfs.h
+++ b/lfs.h
@@ -260,8 +260,9 @@ typedef struct lfs_superblock {
 
 typedef struct lfs_free {
     lfs_block_t begin;
-    lfs_block_t end;
+    lfs_block_t size;
     lfs_block_t off;
+    lfs_block_t ack;
     uint32_t *buffer;
 } lfs_free_t;
 
diff --git a/tests/test_alloc.sh b/tests/test_alloc.sh
index aaae655..493270d 100755
--- a/tests/test_alloc.sh
+++ b/tests/test_alloc.sh
@@ -266,6 +266,40 @@ tests/test.py << TEST
     lfs_mkdir(&lfs, "exhaustiondir2") => LFS_ERR_NOSPC;
 TEST
 
+echo "--- Split dir test ---"
+rm -rf blocks
+tests/test.py << TEST
+    lfs_format(&lfs, &cfg) => 0;
+TEST
+tests/test.py << TEST
+    lfs_mount(&lfs, &cfg) => 0;
+
+    // create one block whole for half a directory
+    lfs_file_open(&lfs, &file[0], "bump", LFS_O_WRONLY | LFS_O_CREAT) => 0;
+    lfs_file_write(&lfs, &file[0], (void*)"hi", 2) => 2;
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < (cfg.block_count-6)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    // open whole
+    lfs_remove(&lfs, "bump") => 0;
+
+    lfs_mkdir(&lfs, "splitdir") => 0;
+    lfs_file_open(&lfs, &file[0], "splitdir/bump",
+            LFS_O_WRONLY | LFS_O_CREAT) => 0;
+    lfs_file_write(&lfs, &file[0], buffer, size) => LFS_ERR_NOSPC;
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    lfs_unmount(&lfs) => 0;
+TEST
 
 echo "--- Results ---"
 tests/stats.py