diff --git a/src/file.c b/src/file.c
index ff5b8fc..c45fd6c 100644
--- a/src/file.c
+++ b/src/file.c
@@ -36,23 +36,26 @@ CosmsCoreFileError cosms_core_file_open(struct cosms_core_file *file, const char
     
     if (mode & COSMS_CORE_FILE_MODE_APPEND) {
         flags |= O_APPEND;
-    } else {
-        flags |= O_TRUNC;
-        if (mode & COSMS_CORE_FILE_MODE_CREATE) {
-            flags |= O_CREAT;
-        }
+    } else if (mode & COSMS_CORE_FILE_MODE_CREATE) {
+        flags |= (O_TRUNC | O_CREAT);
     }
 
+    #ifdef O_LARGEFILE
     struct stat file_stat;
     if (stat(path, &file_stat) != 0) {
+        if (errno == ENOENT) {
+            return COSMS_CORE_FILE_NOT_FOUND;
+        }
+        
         return COSMS_CORE_FILE_COULD_NOT_READ_SIZE;
     }
-
+    
     if (file_stat.st_size > COSMS_CORE_FILE_LARGE) {
         flags |= O_LARGEFILE;
     }
+    #endif
 
-    file->native_file = open(path, flags);
+    file->native_file = open(path, flags, 0644);
     if (file->native_file == -1) {
         switch(errno) {
             case ENOENT: 
@@ -217,7 +220,7 @@ CosmsCoreFileError cosms_core_file_read_all(struct cosms_core_file *file, char *
             current_bytes_to_read = (unsigned int)remaining_bytes;
         }
 
-        int read_bytes = read(file, (*buffer) + (file_stat.st_size - remaining_bytes), current_bytes_to_read);
+        int read_bytes = read(file->native_file, (*buffer) + (file_stat.st_size - remaining_bytes), current_bytes_to_read);
         if (read_bytes == -1) {
             free(*buffer);
             return COSMS_CORE_FILE_FAILED_TO_READ;
@@ -309,7 +312,7 @@ CosmsCoreFileError cosms_core_file_write_all(struct cosms_core_file *file, char
             current_bytes_to_write = (unsigned int)remaining_bytes;
         }
 
-        int written_bytes = write(file->native_file, content + (bytes_to_write - remaining_bytes), current_bytes_to_write);
+        int written_bytes = write(file->native_file, buffer + (bytes_to_write - remaining_bytes), current_bytes_to_write);
         if (written_bytes == -1) {
             return COSMS_CORE_FILE_FAILED_TO_WRITE;
         }
diff --git a/tests/data/large-file.txt b/tests/data/large-file.txt
index d4c5011..d6cf58d 100644
Binary files a/tests/data/large-file.txt and b/tests/data/large-file.txt differ
diff --git a/tests/unit/file.c b/tests/unit/file.c
index b95958c..a80a0cc 100644
--- a/tests/unit/file.c
+++ b/tests/unit/file.c
@@ -170,7 +170,7 @@ COSMS_CORE_TEST_TEST(file_close,
 
 COSMS_CORE_TEST_TEST(file_close_non_existing_file, 
     struct cosms_core_file file;
-    file.native_file = 0;
+    file.native_file = -1;
 
     CosmsCoreFileError error = cosms_core_file_close(&file);
     if (error != COSMS_CORE_FILE_INVALID_FILE) {
@@ -236,7 +236,7 @@ COSMS_CORE_TEST_TEST(file_size_large,
 
 COSMS_CORE_TEST_TEST(file_size_non_existing_file, 
     struct cosms_core_file file;
-    file.native_file = 0;
+    file.native_file = -1;
         
     unsigned long long size = 0;
     CosmsCoreFileError error = cosms_core_file_get_size(&file, &size);
@@ -330,7 +330,7 @@ COSMS_CORE_TEST_TEST(file_read_large_file,
 COSMS_CORE_TEST_TEST(file_read_non_existing_file, 
     struct cosms_core_file file;
     file.mode = COSMS_CORE_FILE_MODE_READ;
-    file.native_file = 0;
+    file.native_file = -1;
 
     unsigned int bytes_to_read = 13;
     unsigned int bytes_read = 0;
@@ -347,7 +347,7 @@ COSMS_CORE_TEST_TEST(file_read_non_existing_file,
 COSMS_CORE_TEST_TEST(file_read_full_non_existing_file,
     struct cosms_core_file file;
     file.mode = COSMS_CORE_FILE_MODE_READ;
-    file.native_file = 0;
+    file.native_file = -1;
 
     unsigned long long bytes_read = 0;
     char *buffer = NULL;
@@ -665,7 +665,6 @@ COSMS_CORE_TEST_TEST(file_write_using_wrong_mode,
 
     error = cosms_core_file_close(&file);
     if (error != COSMS_CORE_FILE_OK) {
-        free(write_buffer);
         return cosms_core_file_error_string(error);
     }