diff --git a/.azure-pipelines/azure-pipelines-osx.yml b/.azure-pipelines/azure-pipelines-osx.yml
index 282a8acfd..beeafce57 100644
--- a/.azure-pipelines/azure-pipelines-osx.yml
+++ b/.azure-pipelines/azure-pipelines-osx.yml
@@ -2,10 +2,10 @@ jobs:
   - job: 'OSX'
     strategy:
       matrix:
-        macOS_10_14:
-          image_name: 'macOS-10.14'
         macOS_10_15:
           image_name: 'macOS-10.15'
+        macOS_11:
+          image_name: 'macOS-11'
     pool:
       vmImage: $(image_name)
     variables:
diff --git a/.azure-pipelines/azure-pipelines-win.yml b/.azure-pipelines/azure-pipelines-win.yml
index 9c0ff6f56..86d76bbad 100644
--- a/.azure-pipelines/azure-pipelines-win.yml
+++ b/.azure-pipelines/azure-pipelines-win.yml
@@ -31,16 +31,18 @@ jobs:
           conda info
         displayName: "Configure Miniconda"
 
+      - script:
+          conda install mamba
       # Create conda enviroment
       # Note: conda activate doesn't work here, because it creates a new shell!
       - script: |
-          conda install cmake==3.14.0 ^
+          mamba install cmake==3.14.0 ^
                         ninja ^
-                        doctest ^
+                        doctest==2.4.7 ^
                         nlohmann_json ^
                         xtl==0.7.0 ^
                         xsimd==8.0.3 ^
-                        python=3.6
+                        python=3.9
           conda list
         displayName: "Install conda packages"
 
diff --git a/environment-dev.yml b/environment-dev.yml
index f4ea820a2..b12fe94ce 100644
--- a/environment-dev.yml
+++ b/environment-dev.yml
@@ -6,4 +6,4 @@ dependencies:
   - xtl=0.7.0
   - xsimd=8.0.3
   - nlohmann_json
-  - doctest
+  - doctest=2.4.7