diff --git a/pythonping/__init__.py b/pythonping/__init__.py
index 2b3c29e..bb52fea 100644
--- a/pythonping/__init__.py
+++ b/pythonping/__init__.py
@@ -5,7 +5,7 @@
 
 
 # this needs to be available across all thread usages and will hold ints
-SEED_IDs = []
+SEED_IDs = set()
 
 
 def ping(target,
@@ -74,15 +74,16 @@ def ping(target,
         # seed_id needs to be less than or equal to 65535 (as original code was seed_id = getpid() & 0xFFFF)
         seed_id = randint(0x1, 0xFFFF)
         if seed_id not in SEED_IDs:
-            SEED_IDs.append(seed_id)
+            SEED_IDs.add(seed_id)
             break
 
+    try:
+        comm = executor.Communicator(target, provider, timeout, interval, socket_options=options, verbose=verbose, output=out,
+                                     seed_id=seed_id, source=source, repr_format=out_format)
 
-    comm = executor.Communicator(target, provider, timeout, interval, socket_options=options, verbose=verbose, output=out,
-                                 seed_id=seed_id, source=source, repr_format=out_format)
+        comm.run(match_payloads=match)
 
-    comm.run(match_payloads=match)
-
-    SEED_IDs.remove(seed_id)
+    finally:
+        SEED_IDs.remove(seed_id)
 
     return comm.responses