diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 5cee5568623..5e70fe270ea 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -108,7 +108,7 @@ stages:
           - bash: |
               set -e
               python -m pip install --progress-bar off --upgrade pip
-              python -m pip install --progress-bar off "mne-qt-browser[opengl] @ git+https://github.com/mne-tools/mne-qt-browser.git@main" pyvista scikit-learn pytest-error-for-skips python-picard "PyQt6!=6.5.1" qtpy nibabel sphinx-gallery
+              python -m pip install --progress-bar off "mne-qt-browser[opengl] @ git+https://github.com/mne-tools/mne-qt-browser.git@main" pyvista scikit-learn pytest-error-for-skips python-picard "PyQt6!=6.5.1" "PyQt6-Qt6!=6.6.1" qtpy nibabel sphinx-gallery
               python -m pip uninstall -yq mne
               python -m pip install --progress-bar off --upgrade -e .[test]
             displayName: 'Install dependencies with pip'
@@ -117,10 +117,9 @@ stages:
               mne sys_info -pd
               mne sys_info -pd | grep "qtpy .*(PyQt6=.*)$"
             displayName: Print config
-          # Uncomment if "xcb not found" Qt errors/segfaults come up again
-          # - bash: |
-          #     set -e
-          #     LD_DEBUG=libs python -c "from PyQt6.QtWidgets import QApplication, QWidget; app = QApplication([]); import matplotlib; matplotlib.use('QtAgg'); import matplotlib.pyplot as plt; plt.figure()"
+          - bash: |
+              set -e
+              LD_DEBUG=libs python -c "from PyQt6.QtWidgets import QApplication, QWidget; app = QApplication([]); import matplotlib; matplotlib.use('QtAgg'); import matplotlib.pyplot as plt; plt.figure()"
           - bash: source tools/get_testing_version.sh
             displayName: 'Get testing version'
           - task: Cache@2
@@ -188,9 +187,9 @@ stages:
             displayName: 'Get test data'
           - bash: |
               set -e
-              python -m pip install PyQt6
-              # Uncomment if "xcb not found" Qt errors/segfaults come up again
-              # LD_DEBUG=libs python -c "from PyQt6.QtWidgets import QApplication, QWidget; app = QApplication([]); import matplotlib; matplotlib.use('QtAgg'); import matplotlib.pyplot as plt; plt.figure()"
+              python -m pip install PyQt6 "PyQt6-Qt6!=6.6.1"
+              LD_DEBUG=libs python -c "from PyQt6.QtWidgets import QApplication, QWidget; app = QApplication([]); import matplotlib; matplotlib.use('QtAgg'); import matplotlib.pyplot as plt; plt.figure()"
+          - bash: |
               mne sys_info -pd
               mne sys_info -pd | grep "qtpy .* (PyQt6=.*)$"
               PYTEST_QT_API=PyQt6 pytest -m "not slowtest" ${TEST_OPTIONS}
diff --git a/pyproject.toml b/pyproject.toml
index bd1b3f2ac32..daba4d874fe 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -60,6 +60,7 @@ full = [
     "mne[hdf5]",
     "qtpy",
     "PyQt6",
+    "PyQt6-Qt6!=6.6.1",
     "pyobjc-framework-Cocoa>=5.2.0; platform_system=='Darwin'",
     "sip",
     "scikit-learn",
diff --git a/tools/azure_dependencies.sh b/tools/azure_dependencies.sh
index 3feb0f2df35..32b51e631f7 100755
--- a/tools/azure_dependencies.sh
+++ b/tools/azure_dependencies.sh
@@ -6,7 +6,7 @@ if [ "${TEST_MODE}" == "pip" ]; then
 	python -m pip install --only-binary="numba,llvmlite,numpy,scipy,vtk" -e .[test,full]
 elif [ "${TEST_MODE}" == "pip-pre" ]; then
 	STD_ARGS="$STD_ARGS --pre"
-	python -m pip install $STD_ARGS --only-binary ":all:" --extra-index-url "https://www.riverbankcomputing.com/pypi/simple" PyQt6 PyQt6-sip PyQt6-Qt6
+	python -m pip install $STD_ARGS --only-binary ":all:" --extra-index-url "https://www.riverbankcomputing.com/pypi/simple" PyQt6 PyQt6-sip PyQt6-Qt6 "PyQt6-Qt6!=6.6.1"
 	echo "Numpy etc."
 	# See github_actions_dependencies.sh for comments
 	python -m pip install $STD_ARGS --only-binary "numpy" numpy
diff --git a/tools/github_actions_dependencies.sh b/tools/github_actions_dependencies.sh
index 0c0069cc1eb..0c4185d6a04 100755
--- a/tools/github_actions_dependencies.sh
+++ b/tools/github_actions_dependencies.sh
@@ -22,7 +22,7 @@ else
 	echo "Numpy"
 	pip uninstall -yq numpy
 	echo "PyQt6"
-	pip install $STD_ARGS --only-binary ":all:" --default-timeout=60 --extra-index-url https://www.riverbankcomputing.com/pypi/simple PyQt6
+	pip install $STD_ARGS --only-binary ":all:" --default-timeout=60 --extra-index-url https://www.riverbankcomputing.com/pypi/simple PyQt6 "PyQt6-Qt6!=6.6.1"
 	echo "NumPy/SciPy/pandas etc."
 	pip install $STD_ARGS --only-binary ":all:" --default-timeout=60 --extra-index-url "https://pypi.anaconda.org/scientific-python-nightly-wheels/simple" "numpy>=2.0.0.dev0" "scipy>=1.12.0.dev0" scikit-learn matplotlib pillow pandas statsmodels
 	# No dipy, h5py, openmeeg, python-picard (needs numexpr) until they update to NumPy 2.0 compat