diff --git a/src/spiffs.h b/src/spiffs.h
index c9a7865..58e49fb 100644
--- a/src/spiffs.h
+++ b/src/spiffs.h
@@ -501,7 +501,7 @@ s32_t SPIFFS_fremove(spiffs *fs, spiffs_file fh);
  * @param fs            the file system struct
  * @param fh            the filehandle of the file to truncate
  * @param new_size      the new size, must be less than existing file size
- * @retval s32_t        error code
+ * @returns 0 on success, error code otherwise
  */
 s32_t SPIFFS_ftruncate(spiffs* fs, spiffs_file fh, u32_t new_size);
 
diff --git a/src/spiffs_hydrogen.c b/src/spiffs_hydrogen.c
index e937fdf..bfeb3cf 100644
--- a/src/spiffs_hydrogen.c
+++ b/src/spiffs_hydrogen.c
@@ -748,7 +748,7 @@ s32_t SPIFFS_ftruncate(spiffs* fs, spiffs_file fh, u32_t new_size) {
   spiffs_fflush_cache(fs, fh);
 #endif
 
-  s32_t file_size = (fd->size == SPIFFS_UNDEFINED_LEN) ? 0 : fd->size;
+  u32_t file_size = (fd->size == SPIFFS_UNDEFINED_LEN) ? 0 : fd->size;
   if (new_size == file_size) {
     res = SPIFFS_OK;
   } else if (new_size > file_size) {
diff --git a/src/test/test_hydrogen.c b/src/test/test_hydrogen.c
index 52126b2..72aea74 100644
--- a/src/test/test_hydrogen.c
+++ b/src/test/test_hydrogen.c
@@ -1003,6 +1003,65 @@ TEST(truncate_big_file)
 }
 TEST_END
 
+TEST(ftruncate_file)
+{
+  int truncated_len = 0;
+  char input[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+  char output[sizeof(input)];
+
+  spiffs_file fd = SPIFFS_open(FS, "ftruncate", SPIFFS_WRONLY | SPIFFS_CREAT | SPIFFS_TRUNC , 0);
+  TEST_CHECK(fd > 0);
+  TEST_CHECK_EQ(strlen(input), SPIFFS_write(FS, fd, input, strlen(input)));
+
+  // Extending file beyond size is not supported
+  TEST_CHECK_EQ(SPIFFS_ERR_END_OF_OBJECT, SPIFFS_ftruncate(FS, fd, strlen(input) + 1));
+  TEST_CHECK_EQ(SPIFFS_ERR_END_OF_OBJECT, SPIFFS_ftruncate(FS, fd, -1));
+
+  // Truncating should succeed
+  const char truncated_1[] = "ABCDEFGHIJ";
+  truncated_len = strlen(truncated_1);
+  TEST_CHECK_EQ(0, SPIFFS_ftruncate(FS, fd, truncated_len));
+  TEST_CHECK_EQ(0, SPIFFS_close(FS, fd));
+
+  // open file for reading and validate the content
+  fd = SPIFFS_open(FS, "ftruncate", SPIFFS_RDONLY, 0);
+  TEST_CHECK(fd > 0);
+  memset(output, 0, sizeof(output));
+  TEST_CHECK_EQ(truncated_len, SPIFFS_read(FS, fd, output, sizeof(output)));
+  TEST_CHECK_EQ(0, strncmp(truncated_1, output, truncated_len));
+  TEST_CHECK_EQ(0, SPIFFS_close(FS, fd));
+
+  // further truncate the file
+  fd = SPIFFS_open(FS, "ftruncate", SPIFFS_WRONLY, 0);
+  TEST_CHECK(fd > 0);
+  // Once truncated, the new file size should be the basis
+  // whether truncation should succeed or not
+  TEST_CHECK_EQ(SPIFFS_ERR_END_OF_OBJECT, SPIFFS_ftruncate(FS, fd, truncated_len + 1));
+  TEST_CHECK_EQ(SPIFFS_ERR_END_OF_OBJECT, SPIFFS_ftruncate(FS, fd, strlen(input)));
+  TEST_CHECK_EQ(SPIFFS_ERR_END_OF_OBJECT, SPIFFS_ftruncate(FS, fd, strlen(input) + 1));
+  TEST_CHECK_EQ(SPIFFS_ERR_END_OF_OBJECT, SPIFFS_ftruncate(FS, fd, -1));
+
+  // Truncating a truncated file should succeed
+  const char truncated_2[] = "ABCDE";
+  truncated_len = strlen(truncated_2);
+
+  TEST_CHECK_EQ(0, SPIFFS_ftruncate(FS, fd, truncated_len));
+  TEST_CHECK_EQ(0, SPIFFS_close(FS, fd));
+
+  // open file for reading and validate the content
+  fd = SPIFFS_open(FS, "ftruncate", SPIFFS_RDONLY, 0);
+  TEST_CHECK(fd > 0);
+
+  memset(output, 0, sizeof(output));
+
+  TEST_CHECK_EQ(truncated_len, SPIFFS_read(FS, fd, output, sizeof(output)));
+  TEST_CHECK_EQ(0, strncmp(truncated_2, output, truncated_len));
+
+  TEST_CHECK_EQ(0, SPIFFS_close(FS, fd));
+
+  return TEST_RES_OK;
+}
+TEST_END
 
 TEST(simultaneous_write) {
   int res = SPIFFS_creat(FS, "simul1", 0);
@@ -2471,6 +2530,7 @@ SUITE_TESTS(hydrogen_tests)
   ADD_TEST(write_big_file_chunks_huge)
   ADD_TEST(write_big_files_chunks_huge)
   ADD_TEST(truncate_big_file)
+  ADD_TEST(ftruncate_file)
   ADD_TEST(simultaneous_write)
   ADD_TEST(simultaneous_write_append)
   ADD_TEST(file_uniqueness)