diff --git a/appveyor.yml b/appveyor.yml
index b62f8b7d8..9cfad489b 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -7,14 +7,19 @@ environment:
   matrix:
     - PYTHON_VERSION: 3.5
       MINICONDA: C:\Miniconda35-x64
+      MPL_VERSION: 3.0.0
     - PYTHON_VERSION: 3.6
-      MINICONDA: C:\Miniconda36-x64
+      MINICONDA: C:\Miniconda3-x64
+      MPL_VERSION: 3.3.4
     - PYTHON_VERSION: 3.7
-      MINICONDA: C:\Miniconda36-x64
+      MINICONDA: C:\Miniconda3-x64
+      MPL_VERSION: 3.3.4
     - PYTHON_VERSION: 3.8
-      MINICONDA: C:\Miniconda36-x64
+      MINICONDA: C:\Miniconda3-x64
+      MPL_VERSION: 3.3.4
     - PYTHON_VERSION: 3.9
-      MINICONDA: C:\Miniconda36-x64
+      MINICONDA: C:\Miniconda3-x64
+      MPL_VERSION: 3.3.4
 
 #configuration:
 #  - Debug
@@ -25,7 +30,8 @@ install:
  - conda config --set always_yes yes --set changeps1 no
  - conda update -q conda
  - conda info -a
- - "conda create -q -n build-environment python=%PYTHON_VERSION% numpy scipy matplotlib"
+# github issue #955: freeze build version of matplotlib
+ - "conda create -q -n build-environment python=%PYTHON_VERSION% numpy scipy matplotlib=%MPL_VERSION%"
  - activate build-environment
  # We need wheel installed to build wheels
  - python -m pip install wheel
diff --git a/setup.py b/setup.py
index 73bfc0356..b79a0d12a 100644
--- a/setup.py
+++ b/setup.py
@@ -118,8 +118,10 @@ def ismac():
     ext_mods = []
 
 install_requirements = ['numpy>=1.7', 'six', 'paramz>=0.9.0', 'cython>=0.29']
+matplotlib_version = 'matplotlib==3.3.4'
 if sys.version_info < (3, 6):
     install_requirements += ['scipy>=1.3.0,<1.5.0']
+    matplotlib_version = 'matplotlib==3.0.0'
 else:
     install_requirements += ['scipy>=1.3.0']
 
@@ -174,7 +176,8 @@ def ismac():
                         'optional':['mpi4py',
                                     'ipython>=4.0.0',
                                     ],
-                        'plotting':['matplotlib >= 3.0',
+                        #matplotlib Version see github issue #955
+                        'plotting':[matplotlib_version,
                                     'plotly >= 1.8.6'],
                         'notebook':['jupyter_client >= 4.0.6',
                                     'ipywidgets >= 4.0.3',