diff --git a/hypertools/plot/backend.py b/hypertools/plot/backend.py
index 20c196f6..45b1f6f1 100644
--- a/hypertools/plot/backend.py
+++ b/hypertools/plot/backend.py
@@ -527,6 +527,7 @@ def _switch_backend_notebook(backend):
             IPYTHON_INSTANCE.run_line_magic('matplotlib', '-l')
 
     output_msg = tmp_stdout.getvalue().strip()
+    tmp_stdout.close()
     if exc is not None:
         # just in case something else was somehow sent to stdout while
         # redirected, or if we managed to catch a different KeyError
diff --git a/requirements.txt b/requirements.txt
index 0671409a..d4f938de 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 PPCA>=0.0.2
-scikit-learn>=0.19.1,!=0.22
+scikit-learn>=0.19.1,!=0.22,<0.24
 pandas>=0.18.0
 seaborn>=0.8.1
 matplotlib>=1.5.1