diff --git a/api.md b/api.md
index e9b25d1..62b22b0 100644
--- a/api.md
+++ b/api.md
@@ -26,6 +26,13 @@ type MappingProtocol* = enum
   Direct   ## no mapping needed, local address is already public
 ```
 
+```nim
+type ProtocolFilter* {.pure.} = enum
+  Any   ## try all protocols (default)
+  PCP   ## PCP/NAT-PMP only
+  UPnP  ## UPnP only
+```
+
 ```nim
 type PlumMapping* = object
   protocol*: PlumProtocol        ## IP protocol (TCP/UDP)
@@ -55,7 +62,8 @@ proc init*(
     logLevel: plum_log_level_t = PLUM_LOG_LEVEL_NONE,
     discoverTimeout: int = 0,
     mappingTimeout: int = 0,
-    recheckPeriod: int = 0
+    recheckPeriod: int = 0,
+    protocol: ProtocolFilter = ProtocolFilter.Any
 ): Result[void, string]
 ```
 
@@ -65,6 +73,7 @@ Initializes the library and starts the internal thread. Must be called before an
 - `discoverTimeout`: how long to probe for a NAT device, in ms (default: 10000)
 - `mappingTimeout`: how long to wait for a mapping response, in ms (default: 10000)
 - `recheckPeriod`: interval between periodic mapping rechecks, in ms (default: 300000)
+- `protocol`: restrict discovery to a single family (`ProtocolFilter.PCP` for PCP/NAT-PMP, `ProtocolFilter.UPnP` for UPnP); `ProtocolFilter.Any` tries all (default)
 
 ### cleanup
 
diff --git a/libplum/libplum.nim b/libplum/libplum.nim
index d0ce609..199b990 100644
--- a/libplum/libplum.nim
+++ b/libplum/libplum.nim
@@ -66,6 +66,13 @@ type
     PLUM_IP_PROTOCOL_TCP = 0
     PLUM_IP_PROTOCOL_UDP = 1
 
+  plum_protocol_t* {.
+    importc: "plum_protocol_t", header: "plum.h", size: sizeof(cint)
+  .} = enum
+    PLUM_PROTOCOL_ANY = 0
+    PLUM_PROTOCOL_PCP = 1
+    PLUM_PROTOCOL_UPNP = 2
+
   plum_state_t* {.importc: "plum_state_t", header: "plum.h", size: sizeof(cint).} = enum
     PLUM_STATE_DESTROYED = 0
     PLUM_STATE_PENDING = 1
@@ -96,6 +103,8 @@ type
       # msecs, 0 means use default (10000)
     recheck_period* {.importc: "recheck_period".}: cint
       # msecs, 0 means use default (300000)
+    protocol* {.importc: "protocol".}: plum_protocol_t
+      # PLUM_PROTOCOL_ANY means try all
 
   # Define the mapping struct, passed by copy (usual for struct).
   # The user_ptr is a pointer to the MappingHandle in order to receive the result
diff --git a/libplum/plum.nim b/libplum/plum.nim
index 65b3aad..7c72e85 100644
--- a/libplum/plum.nim
+++ b/libplum/plum.nim
@@ -37,6 +37,11 @@ type
     TCP = PLUM_IP_PROTOCOL_TCP.int
     UDP = PLUM_IP_PROTOCOL_UDP.int
 
+  ProtocolFilter* {.pure.} = enum
+    Any = PLUM_PROTOCOL_ANY.int
+    PCP = PLUM_PROTOCOL_PCP.int
+    UPnP = PLUM_PROTOCOL_UPNP.int
+
   PlumLogLevel* {.pure.} = enum
     Verbose = PLUM_LOG_LEVEL_VERBOSE.int
     Debug = PLUM_LOG_LEVEL_DEBUG.int
@@ -161,8 +166,11 @@ proc init*(
     discoverTimeout: int32 = 0,
     mappingTimeout: int32 = 0,
     recheckPeriod: int32 = 0,
+    protocol: ProtocolFilter = ProtocolFilter.Any,
 ): Result[void, string] =
   ## init MUST be called to setup internal plum thread (plum_init).
+  ## protocol restricts discovery to a single family (PCP/NAT-PMP or UPnP);
+  ## ProtocolFilter.Any tries all.
 
   var config = plum_config_t(
     log_level: plum_log_level_t(logLevel.int),
@@ -171,6 +179,7 @@ proc init*(
     discover_timeout: discoverTimeout.cint,
     mapping_timeout: mappingTimeout.cint,
     recheck_period: recheckPeriod.cint,
+    protocol: plum_protocol_t(protocol.int),
   )
 
   let res = plum_init(addr config)
diff --git a/tests/test_plum.nim b/tests/test_plum.nim
index 7ab7f13..b2e2fea 100644
--- a/tests/test_plum.nim
+++ b/tests/test_plum.nim
@@ -210,3 +210,40 @@ when miniupnp_protocol != "":
       # no destroyMapping on purpose: cleanup must release everything
       check cleanup().isOk()
       check activeMappingCount() == 0
+
+    # miniupnpd in the pcp container also serves UPnP, so a UPnP filter must
+    # override the default PCP-first selection.
+    when miniupnp_protocol == "pcp":
+      test "protocol filter selects UPnP even when PCP is available":
+        require init(
+          discoverTimeout = discoverMs.int32,
+          logLevel = logLevel,
+          protocol = ProtocolFilter.UPnP,
+        )
+          .isOk()
+        defer:
+          discard cleanup()
+
+        let r = waitFor createMapping(TCP, 8111, timeout = mappingTimeout)
+        require r.isOk()
+        let res = r.value
+        defer:
+          destroyMapping(res.id)
+
+        check res.mapping.mappingProtocol == UPnP
+
+    # miniupnpd in the upnp container has PCP/NAT-PMP disabled, so a PCP filter
+    # must not fall back to UPnP: the mapping cannot succeed.
+    when miniupnp_protocol == "upnp":
+      test "protocol filter PCP does not fall back to UPnP":
+        require init(
+          discoverTimeout = discoverMs.int32,
+          logLevel = logLevel,
+          protocol = ProtocolFilter.PCP,
+        )
+          .isOk()
+        defer:
+          discard cleanup()
+
+        let r = waitFor createMapping(TCP, 8112, timeout = mappingTimeout)
+        check r.isErr()