--- a/eric6/eric6_doc.py	Sun Apr 11 16:53:48 2021 +0200
+++ b/eric6/eric6_doc.py	Sun Apr 11 18:45:10 2021 +0200
@@ -205,9 +205,8 @@
         elif k in ["-c", "--style-sheet"]:
             stylesheetFile = v
         elif k in ["-t", "--extension"]:
-            if v.strip():
-                if not v.startswith("."):
-                    v = ".{0}".format(v)
+            if v.strip() and not v.startswith("."):
+                v = ".{0}".format(v)
             supportedExtensions.append(v)
         elif k == "--eol":
             if v.lower() == "cr":