diff --git a/fdroidserver/common.py b/fdroidserver/common.py
index 0a3c8e75..03a8743d 100644
--- a/fdroidserver/common.py
+++ b/fdroidserver/common.py
@@ -184,10 +184,10 @@ def fill_config_defaults(thisconfig):
 
 
 def regsub_file(pattern, repl, path):
-    with open(path, 'r') as f:
+    with open(path, 'rb') as f:
         text = f.read()
-    text = re.sub(pattern, repl, text)
-    with open(path, 'w') as f:
+    text = re.sub(bytes(pattern, 'utf8'), bytes(repl, 'utf8'), text)
+    with open(path, 'wb') as f:
         f.write(text)
 
 
@@ -1724,14 +1724,14 @@ def remove_signing_keys(build_dir):
         if 'build.gradle' in files:
             path = os.path.join(root, 'build.gradle')
 
-            with open(path, "r") as o:
+            with open(path, "r", encoding='utf8') as o:
                 lines = o.readlines()
 
             changed = False
 
             opened = 0
             i = 0
-            with open(path, "w") as o:
+            with open(path, "w", encoding='utf8') as o:
                 while i < len(lines):
                     line = lines[i]
                     i += 1
diff --git a/fdroidserver/metadata.py b/fdroidserver/metadata.py
index a9be8ef0..ded6cd1a 100644
--- a/fdroidserver/metadata.py
+++ b/fdroidserver/metadata.py
@@ -836,7 +836,7 @@ def get_default_app_info(metadatapath=None):
             for root, dirs, files in os.walk(os.getcwd()):
                 if 'build.gradle' in files:
                     p = os.path.join(root, 'build.gradle')
-                    with open(p) as f:
+                    with open(p, 'rb') as f:
                         data = f.read()
                     m = pattern.search(data)
                     if m:
diff --git a/fdroidserver/scanner.py b/fdroidserver/scanner.py
index 53c938fb..41ecbb50 100644
--- a/fdroidserver/scanner.py
+++ b/fdroidserver/scanner.py
@@ -199,7 +199,7 @@ def scan_source(build_dir, root_dir, build):
             elif ext == 'java':
                 if not os.path.isfile(fp):
                     continue
-                with open(fp, 'r') as f:
+                with open(fp, 'r', encoding='utf8') as f:
                     for line in f:
                         if 'DexClassLoader' in line:
                             count += handleproblem('DexClassLoader', fd, fp)
@@ -208,7 +208,7 @@ def scan_source(build_dir, root_dir, build):
             elif ext == 'gradle':
                 if not os.path.isfile(fp):
                     continue
-                with open(fp, 'r') as f:
+                with open(fp, 'r', encoding='utf8') as f:
                     lines = f.readlines()
                 for i, line in enumerate(lines):
                     if is_used_by_gradle(line):
diff --git a/tests/build.TestCase b/tests/build.TestCase
index b3b90fc3..369c3836 100755
--- a/tests/build.TestCase
+++ b/tests/build.TestCase
@@ -57,13 +57,13 @@ class BuildTest(unittest.TestCase):
         fdroidserver.build.config = {}
         fdroidserver.build.config['build_tools'] = teststring
         fdroidserver.build.adapt_gradle(testsdir)
-        pattern = re.compile("buildToolsVersion[\s=]+'%s'\s+" % teststring)
+        pattern = re.compile(bytes("buildToolsVersion[\s=]+'%s'\s+" % teststring, 'utf8'))
         for p in ('source-files/fdroid/fdroidclient/build.gradle',
                   'source-files/Zillode/syncthing-silk/build.gradle',
                   'source-files/open-keychain/open-keychain/build.gradle',
                   'source-files/osmandapp/osmand/build.gradle',
                   'source-files/open-keychain/open-keychain/OpenKeychain/build.gradle'):
-            with open(os.path.join(testsdir, p), 'r') as f:
+            with open(os.path.join(testsdir, p), 'rb') as f:
                 filedata = f.read()
             self.assertIsNotNone(pattern.search(filedata))