--- firefox-42.0.orig/xpcom/io/nsLocalFileUnix.cpp	2015-10-29 23:18:01.000000000 +0100
+++ firefox-42.0/xpcom/io/nsLocalFileUnix.cpp	2015-12-17 18:31:49.639751737 +0100
@@ -1407,8 +1407,13 @@ nsLocalFile::GetDiskSpaceAvailable(int64
       && dq.dqb_bhardlimit) {
     int64_t QuotaSpaceAvailable = 0;
     // dqb_bhardlimit is count of BLOCK_SIZE blocks, dqb_curspace is bytes
+#if defined(__UCLIBC__)
+    if ((BLOCK_SIZE * dq.dqb_bhardlimit) > dq.dqb_curblocks)
+      QuotaSpaceAvailable = int64_t(fs_buf.F_BSIZE * (dq.dqb_bhardlimit - dq.dqb_curblocks));
+#else
     if ((BLOCK_SIZE * dq.dqb_bhardlimit) > dq.dqb_curspace)
       QuotaSpaceAvailable = int64_t(BLOCK_SIZE * dq.dqb_bhardlimit - dq.dqb_curspace);
+#endif
     if (QuotaSpaceAvailable < *aDiskSpaceAvailable) {
       *aDiskSpaceAvailable = QuotaSpaceAvailable;
     }