diff --git a/gef.py b/gef.py
index 023881259..c8fd7314c 100644
--- a/gef.py
+++ b/gef.py
@@ -6440,7 +6440,7 @@ def do_invoke(self, argv: List[str]) -> None:
             if "all" in argv:
                 tids = [t.num for t in threads]
             else:
-                tids = self.check_thread_ids([int(a) for a in argv])
+                tids = self.check_thread_ids(argv)
         else:
             tids = [current_thread.num]
 
@@ -6523,9 +6523,21 @@ def find_tcache() -> int:
 
     @staticmethod
     def check_thread_ids(tids: List[int]) -> List[int]:
-        """Return the subset of tids that are currently valid."""
-        existing_tids = set(t.num for t in gdb.selected_inferior().threads())
-        return list(set(tids) & existing_tids)
+        """Check the validity, dedup, and return all valid tids."""
+        existing_tids = [t.num for t in gdb.selected_inferior().threads()]
+        valid_tids = set()
+        for tid in tids:
+            try:
+                tid = int(tid)
+            except ValueError:
+                err(f"Invalid thread id {tid:d}")
+                continue
+            if tid in existing_tids:
+                valid_tids.add(tid)
+            else:
+                err(f"Unknown thread {tid}")
+
+        return list(valid_tids)
 
     @staticmethod
     def tcachebin(tcache_base: int, i: int) -> Tuple[Optional[GlibcTcacheChunk], int]:
@@ -6772,11 +6784,11 @@ def do_invoke(self, _: List[str], **kwargs: Any) -> None:
 
         args : argparse.Namespace = kwargs["arguments"]
         if args.registers and args.registers[0]:
-            requested_regs = set(args.registers)
-            valid_regs = set(gef.arch.all_registers) & requested_regs
+            required_regs = set(args.registers)
+            valid_regs = [reg for reg in gef.arch.all_registers if reg in required_regs]
             if valid_regs:
                 regs = valid_regs
-            invalid_regs = requested_regs - valid_regs
+            invalid_regs = [reg for reg in required_regs if reg not in valid_regs]
             if invalid_regs:
                 err(f"invalid registers for architecture: {', '.join(invalid_regs)}")
 
@@ -7358,7 +7370,7 @@ def context_regs(self) -> None:
 
         if self["show_registers_raw"] is False:
             regs = set(gef.arch.all_registers)
-            printable_registers = " ".join(regs - ignored_registers)
+            printable_registers = " ".join(list(regs - ignored_registers))
             gdb.execute(f"registers {printable_registers}")
             return