diff --git a/scapy/arch/windows/__init__.py b/scapy/arch/windows/__init__.py
index 645a086dfd2b4740e549f8c3256522789a6a3888..0d1652e0a0e7177b264e30fd271114d2470c191b 100755
--- a/scapy/arch/windows/__init__.py
+++ b/scapy/arch/windows/__init__.py
@@ -363,9 +363,11 @@ def pcapname(dev):
     try:
         return IFACES.dev_from_name(dev).pcap_name
     except ValueError:
-        # pcap.pcap() will choose a sensible default for sniffing if
-        # iface=None
-        return None
+        if conf.use_pcap:
+            # pcap.pcap() will choose a sensible default for sniffing if
+            # iface=None
+            return None
+        raise
 
 def dev_from_pcapname(pcap_name):
     """Return libdnet/Scapy device name for given pypcap device name"""