diff --git a/auth.py b/auth.py
index d2aab591..a9b83a93 100644
--- a/auth.py
+++ b/auth.py
@@ -130,7 +130,7 @@ def storeBasicCredentials(baseDir: str, nickname: str, password: str) -> bool:
             os.rename(passwordFile + '.new', passwordFile)
         else:
             # append to password file
-            with open(passwordFile, "a") as passfile:
+            with open(passwordFile, 'a+') as passfile:
                 passfile.write(storeStr + '\n')
     else:
         with open(passwordFile, "w") as passfile:
diff --git a/follow.py b/follow.py
index 3c6c6e1d..e14ab804 100644
--- a/follow.py
+++ b/follow.py
@@ -520,7 +520,7 @@ def storeFollowRequest(baseDir: str,
     approveFollowsFilename = accountsDir + '/followrequests.txt'
     if os.path.isfile(approveFollowsFilename):
         if approveHandle not in open(approveFollowsFilename).read():
-            with open(approveFollowsFilename, "a") as fp:
+            with open(approveFollowsFilename, 'a+') as fp:
                 fp.write(approveHandle + '\n')
         else:
             if debug:
diff --git a/inbox.py b/inbox.py
index 692b89c1..e4a27672 100644
--- a/inbox.py
+++ b/inbox.py
@@ -1581,7 +1581,7 @@ def populateReplies(baseDir: str, httpPrefix: str, domain: str,
         if numLines > maxReplies:
             return False
         if messageId not in open(postRepliesFilename).read():
-            repliesFile = open(postRepliesFilename, "a")
+            repliesFile = open(postRepliesFilename, 'a+')
             repliesFile.write(messageId + '\n')
             repliesFile.close()
     else: