diff --git a/requirements-dev.txt b/requirements-dev.txt
index 0be007320..1b13fb116 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -5,10 +5,12 @@ typing_extensions>=4.6.0
 numpy
 fonttools
 pytest
+mypy
 cython
 matplotlib
 pyside6
 Pillow
+PyMuPDF
 sphinx
 sphinx-rtd-theme
 sphinxcontrib-jquery
diff --git a/src/ezdxf/version.py b/src/ezdxf/version.py
index c3006ec2d..499a11b12 100644
--- a/src/ezdxf/version.py
+++ b/src/ezdxf/version.py
@@ -24,5 +24,5 @@
 #   1. bug fix release beta0: VERSION = "0.9.1b0"; version = (0, 9, 1, 'b0')
 #   2. bug fix release: VERSION = "0.9.2"; version = (0, 9, 2, 'release')
 
-version = (1, 3, 1, "a0")
-__version__ = "1.3.1a0"
+version = (1, 3, 1, "b0")
+__version__ = "1.3.1b0"