diff --git a/fdroidserver/common.py b/fdroidserver/common.py
index 19a9abef..d821375a 100644
--- a/fdroidserver/common.py
+++ b/fdroidserver/common.py
@@ -480,10 +480,13 @@ def find_apksigner():
     if not os.path.isdir(build_tools_path):
         return None
     for f in sorted(os.listdir(build_tools_path), reverse=True):
-        if not os.path.isdir(os.path.join(build_tools_path, f)) or not isinstance(LooseVersion(f), int):
+        if not os.path.isdir(os.path.join(build_tools_path, f)):
+            continue
+        try:
+            if LooseVersion(f) < LooseVersion(MINIMUM_APKSIGNER_BUILD_TOOLS_VERSION):
+                return None
+        except TypeError:
             continue
-        if LooseVersion(f) < LooseVersion(MINIMUM_APKSIGNER_BUILD_TOOLS_VERSION):
-            return None
         if os.path.exists(os.path.join(build_tools_path, f, 'apksigner')):
             apksigner = os.path.join(build_tools_path, f, 'apksigner')
             logging.info("Using %s " % apksigner)