diff --git a/pyproject.toml b/pyproject.toml
index 4adc8899a..3fd88606b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,7 +34,7 @@ dependencies = [
     # Please note:
     # using any other msgpack version is not supported by borg development and
     # any feedback related to issues caused by this will be ignored.
-    "msgpack >=1.0.3, <=1.0.8",
+    "msgpack==1.1.0rc1", # ">=1.0.3, <=1.0.8",
     "packaging",
 ]
 
diff --git a/src/borg/helpers/msgpack.py b/src/borg/helpers/msgpack.py
index 7dca66b9a..5c0d1a02b 100644
--- a/src/borg/helpers/msgpack.py
+++ b/src/borg/helpers/msgpack.py
@@ -137,7 +137,7 @@ def is_slow_msgpack():
 def is_supported_msgpack():
     # DO NOT CHANGE OR REMOVE! See also requirements and comments in pyproject.toml.
     import msgpack
-    return (1, 0, 3) <= msgpack.version <= (1, 0, 8) and \
+    return (1, 0, 3) <= msgpack.version <= (1, 1, 1) and \
            msgpack.version not in []  # < add bad releases here to deny list