diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
index 01f974be7..18872a9f9 100644
--- a/.github/workflows/benchmark.yml
+++ b/.github/workflows/benchmark.yml
@@ -24,7 +24,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         python -m pip install pytest
-        if [ -f requirements.txt ]; then pip install --use-feature=2020-resolver -r requirements.txt; fi
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         python setup.py develop
         pip install pytest-benchmark
     - name: Benchmark with pytest
diff --git a/.github/workflows/coveralls.yml b/.github/workflows/coveralls.yml
index a6e7b118d..08b4c4511 100644
--- a/.github/workflows/coveralls.yml
+++ b/.github/workflows/coveralls.yml
@@ -27,7 +27,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         python -m pip install flake8 pytest
-        if [ -f requirements.txt ]; then pip install --use-feature=2020-resolver -r requirements.txt; fi
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         python setup.py develop
         python setup.py build_cannonsim
         pip install pytest-cov
diff --git a/.github/workflows/pdocs.yml b/.github/workflows/pdocs.yml
index 05ec51278..187e9a57b 100644
--- a/.github/workflows/pdocs.yml
+++ b/.github/workflows/pdocs.yml
@@ -21,7 +21,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        if [ -f requirements.txt ]; then pip install --use-feature=2020-resolver -r requirements.txt; fi
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         python setup.py develop
         python setup.py build_cannonsim
         pip install pdoc
diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index e03334370..f7ad37709 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -27,7 +27,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         python -m pip install flake8 pytest
-        if [ -f requirements.txt ]; then pip install --use-feature=2020-resolver -r requirements.txt; fi
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         python setup.py develop
         python setup.py build_cannonsim
         pip install pytest-cov
diff --git a/easyvvuq/analysis/pce_analysis.py b/easyvvuq/analysis/pce_analysis.py
index e73579a6f..85ea70f84 100644
--- a/easyvvuq/analysis/pce_analysis.py
+++ b/easyvvuq/analysis/pce_analysis.py
@@ -108,15 +108,30 @@ def _describe(self, qoi, statistic):
             return np.array([v.upper[0] for _, v in enumerate(
                 self.raw_data['output_distributions'][qoi])])
         elif statistic == '1%':
-            return self.raw_data['percentiles'][qoi]['p01']
+            if isinstance(self.raw_data['percentiles'][qoi]['p01'], np.ndarray):
+                return self.raw_data['percentiles'][qoi]['p01']
+            else:
+                return np.array([self.raw_data['percentiles'][qoi]['p01']])
         elif statistic == '10%':
-            return self.raw_data['percentiles'][qoi]['p10']
+            if isinstance(self.raw_data['percentiles'][qoi]['p10'], np.ndarray):
+                return self.raw_data['percentiles'][qoi]['p10']
+            else:
+                return np.array([self.raw_data['percentiles'][qoi]['p10']])
         elif statistic == '90%':
-            return self.raw_data['percentiles'][qoi]['p90']
+            if isinstance(self.raw_data['percentiles'][qoi]['p90'], np.ndarray):
+                return self.raw_data['percentiles'][qoi]['p90']
+            else:
+                return np.array([self.raw_data['percentiles'][qoi]['p90']])
         elif statistic == '99%':
-            return self.raw_data['percentiles'][qoi]['p99']
+            if isinstance(self.raw_data['percentiles'][qoi]['p99'], np.ndarray):
+                return self.raw_data['percentiles'][qoi]['p99']
+            else:
+                return np.array([self.raw_data['percentiles'][qoi]['p99']])
         elif statistic == 'median':
-            return self.raw_data['percentiles'][qoi]['p50']
+            if isinstance(self.raw_data['percentiles'][qoi]['p50'], np.ndarray):
+                return self.raw_data['percentiles'][qoi]['p50']
+            else:
+                return np.array([self.raw_data['percentiles'][qoi]['p50']])
         else:
             try:
                 return self.raw_data['statistical_moments'][qoi][statistic]
diff --git a/easyvvuq/analysis/results.py b/easyvvuq/analysis/results.py
index 98bb5024b..f9e3b8903 100644
--- a/easyvvuq/analysis/results.py
+++ b/easyvvuq/analysis/results.py
@@ -546,8 +546,9 @@ def plot_moments(
                         self.describe(qoi, 'std'), self.describe(qoi, 'mean') +
                         self.describe(qoi, 'std'), label='std', alpha=alpha)
         ax.plot(xvalues, self.describe(qoi, 'mean'), label='mean')
-        ax.plot(xvalues, self.describe(qoi, '1%'), '--', label='1%', color='black')
-        ax.plot(xvalues, self.describe(qoi, '99%'), '--', label='99%', color='black')
+        if all(v in self.supported_stats() for v in ['1%', '99%']):
+            ax.plot(xvalues, self.describe(qoi, '1%'), '--', label='1%', color='black')
+            ax.plot(xvalues, self.describe(qoi, '99%'), '--', label='99%', color='black')
         ax.grid(True)
         if ylabel is None:
             ax.set_ylabel(qoi)