diff --git a/utils.cc b/utils.cc
index 31b25af..b1e903c 100644
--- a/utils.cc
+++ b/utils.cc
@@ -217,7 +217,8 @@
                const void* buf,
                size_t count,
                off_t offset) {
-  TEST_AND_RETURN_FALSE_ERRNO(fd->Seek(offset, SEEK_SET));
+  TEST_AND_RETURN_FALSE_ERRNO(fd->Seek(offset, SEEK_SET) !=
+                              static_cast<off_t>(-1));
   return WriteAll(fd, buf, count);
 }
 
@@ -240,7 +241,8 @@
 
 bool PReadAll(FileDescriptorPtr fd, void* buf, size_t count, off_t offset,
               ssize_t* out_bytes_read) {
-  TEST_AND_RETURN_FALSE_ERRNO(fd->Seek(offset, SEEK_SET));
+  TEST_AND_RETURN_FALSE_ERRNO(fd->Seek(offset, SEEK_SET) !=
+                              static_cast<off_t>(-1));
   char* c_buf = static_cast<char*>(buf);
   ssize_t bytes_read = 0;
   while (bytes_read < static_cast<ssize_t>(count)) {