diff --git a/opus-Fix-celt-decoder-assertion-when-using-OPUS_CUSTOM.patch b/opus-Fix-celt-decoder-assertion-when-using-OPUS_CUSTOM.patch
new file mode 100644
index 0000000..81dbc71
--- /dev/null
+++ b/opus-Fix-celt-decoder-assertion-when-using-OPUS_CUSTOM.patch
@@ -0,0 +1,41 @@
+From 06a651547f4a197c29b6abc23b530833855ee358 Mon Sep 17 00:00:00 2001
+From: Niclas Olmenius <niclas@voysys.se>
+Date: Wed, 19 Feb 2020 13:58:35 +0100
+Subject: [PATCH] Fix celt decoder assertion when using OPUS_CUSTOM
+
+When using OPUS_CUSTOM, `CELTDecoder->end` can be larger than 21.
+Assert against 25 instead in OPUS_CUSTOM builds.
+
+Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>
+---
+ celt/celt_decoder.c | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/celt/celt_decoder.c b/celt/celt_decoder.c
+index e6efce93..74ca3b74 100644
+--- a/celt/celt_decoder.c
++++ b/celt/celt_decoder.c
+@@ -117,13 +117,19 @@ void validate_celt_decoder(CELTDecoder *st)
+ #ifndef CUSTOM_MODES
+    celt_assert(st->mode == opus_custom_mode_create(48000, 960, NULL));
+    celt_assert(st->overlap == 120);
++   celt_assert(st->end <= 21);
++#else
++/* From Section 4.3 in the spec: "The normal CELT layer uses 21 of those bands,
++   though Opus Custom (see Section 6.2) may use a different number of bands"
++
++   Check if it's within the maximum number of Bark frequency bands instead */
++   celt_assert(st->end <= 25);
+ #endif
+    celt_assert(st->channels == 1 || st->channels == 2);
+    celt_assert(st->stream_channels == 1 || st->stream_channels == 2);
+    celt_assert(st->downsample > 0);
+    celt_assert(st->start == 0 || st->start == 17);
+    celt_assert(st->start < st->end);
+-   celt_assert(st->end <= 21);
+ #ifdef OPUS_ARCHMASK
+    celt_assert(st->arch >= 0);
+    celt_assert(st->arch <= OPUS_ARCHMASK);
+-- 
+2.26.0
+
diff --git a/opus.changes b/opus.changes
index ad95055..bca62b1 100644
--- a/opus.changes
+++ b/opus.changes
@@ -1,3 +1,11 @@
+-------------------------------------------------------------------
+Wed Apr 15 17:38:39 UTC 2020 - Gustavo Pichorim Boiko <gboiko@suse.com>
+
+- Backport of an upstream fix for celt decoder:
+  * opus-Fix-celt-decoder-assertion-when-using-OPUS_CUSTOM.patch: When
+    using OPUS_CUSTOM, `CELTDecoder->end` can be larger than 21.
+    Assert against 25 instead in OPUS_CUSTOM builds.
+
 -------------------------------------------------------------------
 Thu Aug 15 17:37:36 UTC 2019 - Bjørn Lie <bjorn.lie@gmail.com>
 
diff --git a/opus.spec b/opus.spec
index 426880b..54d102e 100644
--- a/opus.spec
+++ b/opus.spec
@@ -1,7 +1,7 @@
 #
 # spec file for package opus
 #
-# Copyright (c) 2019 SUSE LINUX GmbH, Nuernberg, Germany.
+# Copyright (c) 2020 SUSE LLC
 # Copyright (c) 2012 Pascal Bleser <pascal.bleser@opensuse.org>
 #
 # All modifications and additions to the file contributed by third parties
@@ -31,6 +31,8 @@ Source99:       baselibs.conf
 Patch0:         opus-Silk-CNG-adapts-faster.patch
 # PATCH-FIX-UPSTREAM opus-Silk-fix-arm-optimization.patch -- Avoid processing LPC coeffs beyond the given order in NEON optimizations
 Patch1:         opus-Silk-fix-arm-optimization.patch
+# PATCH-FIX-UPSTREAM opus-Fix-celt-decoder-assertion-when-using-OPUS_CUSTOM.patch -- Fix celt decoder assertion when using OPUS_CUSTOM
+Patch2:         opus-Fix-celt-decoder-assertion-when-using-OPUS_CUSTOM.patch
 BuildRequires:  pkgconfig
 
 %description
@@ -61,6 +63,7 @@ technology from Skype's SILK codec and Xiph.Org's CELT codec.
 %setup -q
 %patch0 -p1
 %patch1 -p1
+%patch2 -p1
 
 %build
 %configure \