diff --git a/pdfplumber/page.py b/pdfplumber/page.py
index a20c889..ac94610 100644
--- a/pdfplumber/page.py
+++ b/pdfplumber/page.py
@@ -31,11 +31,21 @@ class Page(Container):
 
         if self.rotation in [90, 270]:
             self.bbox = self.decimalize(
-                (min(m[1], m[3]), min(m[0], m[2]), max(m[1], m[3]), max(m[0], m[2]),)
+                (
+                    min(m[1], m[3]),
+                    min(m[0], m[2]),
+                    max(m[1], m[3]),
+                    max(m[0], m[2]),
+                )
             )
         else:
             self.bbox = self.decimalize(
-                (min(m[0], m[2]), min(m[1], m[3]), max(m[0], m[2]), max(m[1], m[3]),)
+                (
+                    min(m[0], m[2]),
+                    min(m[1], m[3]),
+                    max(m[0], m[2]),
+                    max(m[1], m[3]),
+                )
             )
 
     def decimalize(self, x):
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 46d8893..3ab2792 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,5 +1,5 @@
 pytest
 pytest-cov
 pytest-parallel
-flake8
-black
+flake8==3.8.3
+black==20.8b0