diff --git a/requirements/dev.txt b/requirements/dev.txt
index 1a176e9350..1fa935ca0b 100644
--- a/requirements/dev.txt
+++ b/requirements/dev.txt
@@ -1,9 +1,9 @@
 -r optional.txt
 
 isort>=4.2.3
-pycodestyle==2.3.1
-pydocstyle==2.0.0
-pytest==3.0.7
+pycodestyle==2.7.0
+pydocstyle==6.1.1
+pytest==6.2.4
 pytest-cov
 pytest-xdist
-Sphinx==1.5.5
+Sphinx==4.1.2
diff --git a/requirements/optional.txt b/requirements/optional.txt
index b158de7986..5e25f34588 100644
--- a/requirements/optional.txt
+++ b/requirements/optional.txt
@@ -4,13 +4,13 @@
 # Format support #
 ##################
 BeautifulSoup4>=4.3  # Trados TM
-iniparse==0.4 ;python_version < '3.0'      # INI (ini2po)
-vobject==0.9.4.1       # iCal (ical2po)
+iniparse==0.5 ;python_version < '3.0'      # INI (ini2po)
+vobject==0.9.6.1       # iCal (ical2po)
 
 #aeidon>=0.14        # Subtitles (sub2po)
 # aeidon not available through pip/PyPI,
 # so recording this dependency here is pointless except as a comment
 
-Babel==2.4.0         # Android plurals
+Babel==2.9.1         # Android plurals
 l20n==4.0.0a1        # l20n (l20n2po)
-PyYAML==3.12         # yaml
+PyYAML==5.4.1         # yaml
diff --git a/requirements/recommended.txt b/requirements/recommended.txt
index c58c3515e1..ec562de9d5 100644
--- a/requirements/recommended.txt
+++ b/requirements/recommended.txt
@@ -11,4 +11,4 @@ lxml>=3.5
 python-Levenshtein>=0.12
 
 # Encoding detection
-chardet==3.0.2
+chardet==4.0.0
diff --git a/requirements/required.txt b/requirements/required.txt
index d401e1e70f..6fcbddcacd 100644
--- a/requirements/required.txt
+++ b/requirements/required.txt
@@ -1,4 +1,4 @@
 six>=1.10.0
 
 # Required to provide compatibility for old Virtaal releases:
-diff-match-patch==20121119
+diff-match-patch==20200713