diff --git a/CHANGES b/CHANGES
index 245559d1b..53fb5f9f7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -58,6 +58,13 @@ Attic Changelog
 Here you can see the full list of changes between each Attic release until Borg
 forked from Attic:
 
+Version 0.17
+------------
+
+(bugfix release, released on X)
+- Fix hashindex ARM memory alignment issue (#309)
+- Improve hashindex error messages (#298)
+
 Version 0.16
 ------------
 
diff --git a/borg/_hashindex.c b/borg/_hashindex.c
index 2c3ed01bf..e2589d0b8 100644
--- a/borg/_hashindex.c
+++ b/borg/_hashindex.c
@@ -27,7 +27,6 @@ typedef struct {
 } __attribute__((__packed__)) HashHeader;
 
 typedef struct {
-    void *data;
     void *buckets;
     int num_entries;
     int num_buckets;
@@ -36,7 +35,6 @@ typedef struct {
     off_t bucket_size;
     int lower_limit;
     int upper_limit;
-    off_t data_len;
 } HashIndex;
 
 #define MAGIC "BORG_IDX"
@@ -57,8 +55,10 @@ typedef struct {
 #define BUCKET_MARK_DELETED(index, idx) (*((uint32_t *)(BUCKET_ADDR(index, idx) + index->key_size)) = DELETED)
 #define BUCKET_MARK_EMPTY(index, idx) (*((uint32_t *)(BUCKET_ADDR(index, idx) + index->key_size)) = EMPTY)
 
-#define EPRINTF(msg, ...) fprintf(stderr, "hashindex: " msg "\n", ##__VA_ARGS__)
-#define EPRINTF_PATH(path, msg, ...) fprintf(stderr, "hashindex: %s: " msg "\n", path, ##__VA_ARGS__)
+#define EPRINTF_MSG(msg, ...) fprintf(stderr, "hashindex: " msg "\n", ##__VA_ARGS__)
+#define EPRINTF_MSG_PATH(path, msg, ...) fprintf(stderr, "hashindex: %s: " msg "\n", path, ##__VA_ARGS__)
+#define EPRINTF(msg, ...) fprintf(stderr, "hashindex: " msg "(%s)\n", ##__VA_ARGS__, strerror(errno))
+#define EPRINTF_PATH(path, msg, ...) fprintf(stderr, "hashindex: %s: " msg " (%s)\n", path, ##__VA_ARGS__, strerror(errno))
 
 static HashIndex *hashindex_read(const char *path);
 static int hashindex_write(HashIndex *index, const char *path);
@@ -118,13 +118,11 @@ hashindex_resize(HashIndex *index, int capacity)
     while((key = hashindex_next_key(index, key))) {
         hashindex_set(new, key, hashindex_get(index, key));
     }
-    free(index->data);
-    index->data = new->data;
-    index->data_len = new->data_len;
+    free(index->buckets);
+    index->buckets = new->buckets;
     index->num_buckets = new->num_buckets;
     index->lower_limit = new->lower_limit;
     index->upper_limit = new->upper_limit;
-    index->buckets = new->buckets;
     free(new);
     return 1;
 }
@@ -134,18 +132,22 @@ static HashIndex *
 hashindex_read(const char *path)
 {
     FILE *fd;
-    off_t length;
-    off_t bytes_read;
+    off_t length, buckets_length, bytes_read;
     HashHeader header;
     HashIndex *index = NULL;
 
-    if((fd = fopen(path, "r")) == NULL) {
-        EPRINTF_PATH(path, "fopen failed");
+    if((fd = fopen(path, "rb")) == NULL) {
+        EPRINTF_PATH(path, "fopen for reading failed");
         return NULL;
     }
     bytes_read = fread(&header, 1, sizeof(HashHeader), fd);
     if(bytes_read != sizeof(HashHeader)) {
-        EPRINTF_PATH(path, "fread header failed (expected %ld, got %ld)", sizeof(HashHeader), bytes_read);
+        if(ferror(fd)) {
+            EPRINTF_PATH(path, "fread header failed (expected %ld, got %ld)", sizeof(HashHeader), bytes_read);
+        }
+        else {
+            EPRINTF_MSG_PATH(path, "fread header failed (expected %ld, got %ld)", sizeof(HashHeader), bytes_read);
+        }
         goto fail;
     }
     if(fseek(fd, 0, SEEK_END) < 0) {
@@ -156,43 +158,47 @@ hashindex_read(const char *path)
         EPRINTF_PATH(path, "ftell failed");
         goto fail;
     }
-    if(fseek(fd, 0, SEEK_SET) < 0) {
+    if(fseek(fd, sizeof(HashHeader), SEEK_SET) < 0) {
         EPRINTF_PATH(path, "fseek failed");
         goto fail;
     }
     if(memcmp(header.magic, MAGIC, 8)) {
-        EPRINTF_PATH(path, "Unknown file header");
+        EPRINTF_MSG_PATH(path, "Unknown MAGIC in header");
         goto fail;
     }
-    if(length != sizeof(HashHeader) + (off_t)_le32toh(header.num_buckets) * (header.key_size + header.value_size)) {
-        EPRINTF_PATH(path, "Incorrect file length");
+    buckets_length = (off_t)_le32toh(header.num_buckets) * (header.key_size + header.value_size);
+    if(length != sizeof(HashHeader) + buckets_length) {
+        EPRINTF_MSG_PATH(path, "Incorrect file length (expected %ld, got %ld)", sizeof(HashHeader) + buckets_length, length);
         goto fail;
     }
     if(!(index = malloc(sizeof(HashIndex)))) {
-        EPRINTF_PATH(path, "malloc failed");
+        EPRINTF_PATH(path, "malloc header failed");
         goto fail;
     }
-    if(!(index->data = malloc(length))) {
-        EPRINTF_PATH(path, "malloc failed");
+    if(!(index->buckets = malloc(buckets_length))) {
+        EPRINTF_PATH(path, "malloc buckets failed");
         free(index);
         index = NULL;
         goto fail;
     }
-    bytes_read = fread(index->data, 1, length, fd);
-    if(bytes_read != length) {
-        EPRINTF_PATH(path, "fread hashindex failed (expected %ld, got %ld)", length, bytes_read);
-        free(index->data);
+    bytes_read = fread(index->buckets, 1, buckets_length, fd);
+    if(bytes_read != buckets_length) {
+        if(ferror(fd)) {
+            EPRINTF_PATH(path, "fread buckets failed (expected %ld, got %ld)", buckets_length, bytes_read);
+        }
+        else {
+            EPRINTF_MSG_PATH(path, "fread buckets failed (expected %ld, got %ld)", buckets_length, bytes_read);
+        }
+        free(index->buckets);
         free(index);
         index = NULL;
         goto fail;
     }
-    index->data_len = length;
     index->num_entries = _le32toh(header.num_entries);
     index->num_buckets = _le32toh(header.num_buckets);
     index->key_size = header.key_size;
     index->value_size = header.value_size;
     index->bucket_size = index->key_size + index->value_size;
-    index->buckets = index->data + sizeof(HashHeader);
     index->lower_limit = index->num_buckets > MIN_BUCKETS ? ((int)(index->num_buckets * BUCKET_LOWER_LIMIT)) : 0;
     index->upper_limit = (int)(index->num_buckets * BUCKET_UPPER_LIMIT);
 fail:
@@ -205,20 +211,18 @@ fail:
 static HashIndex *
 hashindex_init(int capacity, int key_size, int value_size)
 {
+    off_t buckets_length;
     HashIndex *index;
-    HashHeader header = {
-        .magic = MAGIC, .num_entries = 0, .key_size = key_size, .value_size = value_size
-    };
     int i;
     capacity = MAX(MIN_BUCKETS, capacity);
 
     if(!(index = malloc(sizeof(HashIndex)))) {
-        EPRINTF("malloc failed");
+        EPRINTF("malloc header failed");
         return NULL;
     }
-    index->data_len = sizeof(HashHeader) + (off_t)capacity * (key_size + value_size);
-    if(!(index->data = calloc(index->data_len, 1))) {
-        EPRINTF("malloc failed");
+    buckets_length = (off_t)capacity * (key_size + value_size);
+    if(!(index->buckets = calloc(buckets_length, 1))) {
+        EPRINTF("malloc buckets failed");
         free(index);
         return NULL;
     }
@@ -229,8 +233,6 @@ hashindex_init(int capacity, int key_size, int value_size)
     index->bucket_size = index->key_size + index->value_size;
     index->lower_limit = index->num_buckets > MIN_BUCKETS ? ((int)(index->num_buckets * BUCKET_LOWER_LIMIT)) : 0;
     index->upper_limit = (int)(index->num_buckets * BUCKET_UPPER_LIMIT);
-    index->buckets = index->data + sizeof(HashHeader);
-    memcpy(index->data, &header, sizeof(HashHeader));
     for(i = 0; i < capacity; i++) {
         BUCKET_MARK_EMPTY(index, i);
     }
@@ -240,25 +242,34 @@ hashindex_init(int capacity, int key_size, int value_size)
 static void
 hashindex_free(HashIndex *index)
 {
-    free(index->data);
+    free(index->buckets);
     free(index);
 }
 
 static int
 hashindex_write(HashIndex *index, const char *path)
 {
+    off_t buckets_length = (off_t)index->num_buckets * index->bucket_size;
     FILE *fd;
+    HashHeader header = {
+        .magic = MAGIC,
+        .num_entries = _htole32(index->num_entries),
+        .num_buckets = _htole32(index->num_buckets),
+        .key_size = index->key_size,
+        .value_size = index->value_size
+    };
     int ret = 1;
 
-    if((fd = fopen(path, "w")) == NULL) {
-        EPRINTF_PATH(path, "open failed");
-        fprintf(stderr, "Failed to open %s for writing\n", path);
+    if((fd = fopen(path, "wb")) == NULL) {
+        EPRINTF_PATH(path, "fopen for writing failed");
         return 0;
     }
-    *((uint32_t *)(index->data + 8)) = _htole32(index->num_entries);
-    *((uint32_t *)(index->data + 12)) = _htole32(index->num_buckets);
-    if(fwrite(index->data, 1, index->data_len, fd) != index->data_len) {
-        EPRINTF_PATH(path, "fwrite failed");
+    if(fwrite(&header, 1, sizeof(header), fd) != sizeof(header)) {
+        EPRINTF_PATH(path, "fwrite header failed");
+        ret = 0;
+    }
+    if(fwrite(index->buckets, 1, buckets_length, fd) != buckets_length) {
+        EPRINTF_PATH(path, "fwrite buckets failed");
         ret = 0;
     }
     if(fclose(fd) < 0) {
@@ -366,4 +377,3 @@ hashindex_summarize(HashIndex *index, long long *total_size, long long *total_cs
     *total_unique_size = unique_size;
     *total_unique_csize = unique_csize;
 }
-
diff --git a/borg/cache.py b/borg/cache.py
index 037a8e76b..573a7f5cc 100644
--- a/borg/cache.py
+++ b/borg/cache.py
@@ -93,7 +93,7 @@ class Cache:
         with open(os.path.join(self.path, 'config'), 'w') as fd:
             config.write(fd)
         ChunkIndex().write(os.path.join(self.path, 'chunks').encode('utf-8'))
-        with open(os.path.join(self.path, 'files'), 'w') as fd:
+        with open(os.path.join(self.path, 'files'), 'wb') as fd:
             pass  # empty file
 
     def destroy(self):
diff --git a/borg/testsuite/archiver.py b/borg/testsuite/archiver.py
index 11efefd3d..b35df2477 100644
--- a/borg/testsuite/archiver.py
+++ b/borg/testsuite/archiver.py
@@ -400,9 +400,9 @@ class ArchiverTestCase(ArchiverTestCaseBase):
         self.cmd('extract', '--dry-run', self.repository_location + '::test')
         self.cmd('check', self.repository_location)
         name = sorted(os.listdir(os.path.join(self.tmpdir, 'repository', 'data', '0')), reverse=True)[0]
-        with open(os.path.join(self.tmpdir, 'repository', 'data', '0', name), 'r+') as fd:
+        with open(os.path.join(self.tmpdir, 'repository', 'data', '0', name), 'r+b') as fd:
             fd.seek(100)
-            fd.write('XXXX')
+            fd.write(b'XXXX')
         self.cmd('check', self.repository_location, exit_code=1)
 
     def test_readonly_repository(self):