diff --git a/src/diffuse/vcs/bzr.py b/src/diffuse/vcs/bzr.py
index e7b4669..3dee6db 100644
--- a/src/diffuse/vcs/bzr.py
+++ b/src/diffuse/vcs/bzr.py
@@ -181,7 +181,7 @@ class Bzr(VcsInterface):
                     result.append(m[k])
         return result
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         return utils.popenRead(
             self.root,
             [
diff --git a/src/diffuse/vcs/cvs.py b/src/diffuse/vcs/cvs.py
index fc90088..8b34bd5 100644
--- a/src/diffuse/vcs/cvs.py
+++ b/src/diffuse/vcs/cvs.py
@@ -86,10 +86,10 @@ class Cvs(VcsInterface):
         # sort the results
         return [modified[k] for k in sorted(modified.keys())]
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         if rev == 'BASE' and not os.path.exists(name):
             # find revision for removed files
-            for s in utils.popenReadLines(
+            lines = utils.popenReadLines(
                 self.root,
                 [
                     prefs.getString('cvs_bin'),
@@ -98,9 +98,10 @@ class Cvs(VcsInterface):
                 ],
                 prefs,
                 'cvs_bash'
-            ):
-                if s.startswith('   Working revision:\t-'):
-                    rev = s.split('\t')[1][1:]
+            )
+            for line in lines:
+                if line.startswith('   Working revision:\t-'):
+                    rev = line.split('\t')[1][1:]
         return utils.popenRead(
             self.root,
             [
diff --git a/src/diffuse/vcs/darcs.py b/src/diffuse/vcs/darcs.py
index 0607f8f..dac7bdd 100644
--- a/src/diffuse/vcs/darcs.py
+++ b/src/diffuse/vcs/darcs.py
@@ -19,6 +19,8 @@
 
 import os
 
+from typing import List, Optional
+
 from diffuse import utils
 from diffuse.preferences import Preferences
 from diffuse.vcs.folder_set import FolderSet
@@ -136,8 +138,8 @@ class Darcs(VcsInterface):
     def getFolderTemplate(self, prefs, names):
         return self._getCommitTemplate(prefs, names, None)
 
-    def getRevision(self, prefs, name, rev):
-        args = [prefs.getString('darcs_bin'), 'show', 'contents']
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
+        args: List[Optional[str]] = [prefs.getString('darcs_bin'), 'show', 'contents']
         try:
             args.extend(['-n', str(int(rev))])
         except ValueError:
diff --git a/src/diffuse/vcs/git.py b/src/diffuse/vcs/git.py
index e741315..46b19e6 100644
--- a/src/diffuse/vcs/git.py
+++ b/src/diffuse/vcs/git.py
@@ -150,7 +150,7 @@ class Git(VcsInterface):
                     result.append(m[k])
         return result
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         relpath = utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/')
         return utils.popenRead(
             self.root,
diff --git a/src/diffuse/vcs/hg.py b/src/diffuse/vcs/hg.py
index 88deb47..7cdb11f 100644
--- a/src/diffuse/vcs/hg.py
+++ b/src/diffuse/vcs/hg.py
@@ -98,7 +98,7 @@ class Hg(VcsInterface):
     def getFolderTemplate(self, prefs, names):
         return self._getCommitTemplate(prefs, names, ['status', '-q'], None)
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         return utils.popenRead(
             self.root,
             [
diff --git a/src/diffuse/vcs/mtn.py b/src/diffuse/vcs/mtn.py
index 749754a..9aefbdb 100644
--- a/src/diffuse/vcs/mtn.py
+++ b/src/diffuse/vcs/mtn.py
@@ -218,7 +218,7 @@ class Mtn(VcsInterface):
                     result.append(m[k])
         return result
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         return utils.popenRead(
             self.root,
             [
diff --git a/src/diffuse/vcs/rcs.py b/src/diffuse/vcs/rcs.py
index f6d721a..d9bda95 100644
--- a/src/diffuse/vcs/rcs.py
+++ b/src/diffuse/vcs/rcs.py
@@ -154,7 +154,7 @@ class Rcs(VcsInterface):
         # sort the results
         return [[(k, r[k]), (k, None)] for k in sorted(r.keys())]
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         return utils.popenRead(
             self.root,
             [
diff --git a/src/diffuse/vcs/svk.py b/src/diffuse/vcs/svk.py
index 5e25e4b..8cf3ca6 100644
--- a/src/diffuse/vcs/svk.py
+++ b/src/diffuse/vcs/svk.py
@@ -22,6 +22,7 @@ import os
 from typing import Optional, Tuple
 
 from diffuse import utils
+from diffuse.preferences import Preferences
 from diffuse.vcs.svn import Svn
 
 
@@ -48,7 +49,7 @@ class Svk(Svn):
             return str(int(rev[:-1]) - 1) + '@'
         return str(int(rev) - 1)
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         relpath = utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/')
         return utils.popenRead(
             self.root,
diff --git a/src/diffuse/vcs/svn.py b/src/diffuse/vcs/svn.py
index 0e4327d..cafd837 100644
--- a/src/diffuse/vcs/svn.py
+++ b/src/diffuse/vcs/svn.py
@@ -272,7 +272,7 @@ class Svn(VcsInterface):
     def getFolderTemplate(self, prefs, names):
         return self._getCommitTemplate(prefs, None, names)
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         vcs_bin = prefs.getString('svn_bin')
         if rev in ['BASE', 'COMMITTED', 'PREV']:
             return utils.popenRead(
diff --git a/src/diffuse/vcs/vcs_interface.py b/src/diffuse/vcs/vcs_interface.py
index 0cef9d3..4ba9504 100644
--- a/src/diffuse/vcs/vcs_interface.py
+++ b/src/diffuse/vcs/vcs_interface.py
@@ -42,5 +42,5 @@ class VcsInterface:
     def getFolderTemplate(self, prefs, names):
         """Indicates which file revisions to display for a set of folders."""
 
-    def getRevision(self, prefs, name, rev):
+    def getRevision(self, prefs: Preferences, name: str, rev: str) -> bytes:
         """Returns the contents of the specified file revision"""