diff --git a/src/syndump.nim b/src/syndump.nim
index 4e5e004..c15fc8f 100644
--- a/src/syndump.nim
+++ b/src/syndump.nim
@@ -29,21 +29,16 @@ proc parsePattern(pr: Assertion): Pattern =
 
 proc inputPattern: Pattern =
   var args = commandLineParams()
-  if args.len != 1:
+  if args.len != 1 or args == @[""]:
     quit "expected a single pattern argument"
   else:
-    var input = pop args
-    if input == "":
-      quit "expected Preserves Pattern on stdin"
-    else:
-      var pr: Assertion
-      try: pr = decodePreserves(input, Cap)
-      except ValueError: discard
-      try: pr = parsePreserves(input, Cap)
-      except ValueError: discard
-      if pr.isFalse:
-        quit "failed to parse Preserves argument"
-      result = parsePattern(pr)
+    var
+      pr: Assertion
+      input = pop args
+    try: pr = parsePreserves(input, Cap)
+    except ValueError:
+      quit "failed to parse Preserves argument"
+    result = parsePattern(pr)
 
 type DumpEntity {.final.} = ref object of Entity
   assertions: Table[Handle, seq[Assertion]]