diff --git a/appveyor.yml b/appveyor.yml
index ca3c868ab..e749d4d58 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -24,7 +24,7 @@ environment:
     - APPVEYOR_BUILD_WORKER_IMAGE: "Visual Studio 2019"
       PYTHON: "C:/Python311-x64"
     # MacOS
-    - APPVEYOR_BUILD_WORKER_IMAGE: "macos-catalina"
+    - APPVEYOR_BUILD_WORKER_IMAGE: "macos-mojave"
       PYTHON: "~/venv3.11"
     # Linux
     - APPVEYOR_BUILD_WORKER_IMAGE: "Ubuntu1804"
@@ -72,7 +72,7 @@ for:
   -
     matrix:
       only:
-        - APPVEYOR_BUILD_WORKER_IMAGE: "macos-catalina"
+        - APPVEYOR_BUILD_WORKER_IMAGE: "macos-mojave"
 
     # Install dependencies
     install:
diff --git a/requirements/requirements_tests.txt b/requirements/requirements_tests.txt
index 78d7ad17a..57334c1b4 100644
--- a/requirements/requirements_tests.txt
+++ b/requirements/requirements_tests.txt
@@ -56,18 +56,16 @@ beautifulsoup4
 lxml
 matplotlib
 networkx
-## spaCy is incompatible with NumPy 2.0
-numpy == 1.26.4
+numpy == 1.26.4 # spaCy is incompatible with NumPy 2.0
 opencc-python-reimplemented
 openpyxl
 pypdf
-pyqt5
+pyqt5==5.15.10 # To be compatible with macOS < 11
 pytest
 python-docx
 python-pptx
 requests
-# Underthesea is incompatible with scikit-learn 1.5
-scikit-learn == 1.4.2
+scikit-learn == 1.4.2 # Underthesea is incompatible with scikit-learn 1.5
 scipy
 wordcloud