diff --git a/src/iosource/PktSrc.cc b/src/iosource/PktSrc.cc
index e4cbfe31e9..8db9db6ef1 100644
--- a/src/iosource/PktSrc.cc
+++ b/src/iosource/PktSrc.cc
@@ -36,9 +36,7 @@ PktSrc::PktSrc()
 
 PktSrc::~PktSrc()
 	{
-	BPF_Program* code;
-	IterCookie* cookie = filters.InitForIteration();
-	while ( (code = filters.NextEntry(cookie)) )
+	for ( auto code : filters )
 		delete code;
 	}
 
@@ -335,16 +333,16 @@ bool PktSrc::PrecompileBPFFilter(int index, const std::string& filter)
 		return 0;
 		}
 
-	// Store it in hash.
-	HashKey* hash = new HashKey(HashKey(bro_int_t(index)));
-	BPF_Program* oldcode = filters.Lookup(hash);
-	if ( oldcode )
-		delete oldcode;
+	// Store it in vector.
+	if ( index >= static_cast<int>(filters.size()) )
+		filters.resize(index + 1);
 
-	filters.Insert(hash, code);
-	delete hash;
+	if ( auto old = filters[index] )
+		delete old;
 
-	return 1;
+	filters[index] = code;
+
+	return true;
 	}
 
 BPF_Program* PktSrc::GetBPFFilter(int index)
@@ -352,10 +350,7 @@ BPF_Program* PktSrc::GetBPFFilter(int index)
 	if ( index < 0 )
 		return 0;
 
-	HashKey* hash = new HashKey(HashKey(bro_int_t(index)));
-	BPF_Program* code = filters.Lookup(hash);
-	delete hash;
-	return code;
+	return (static_cast<int>(filters.size()) > index ? filters[index] : 0);
 	}
 
 bool PktSrc::ApplyBPFFilter(int index, const struct pcap_pkthdr *hdr, const u_char *pkt)
diff --git a/src/iosource/PktSrc.h b/src/iosource/PktSrc.h
index 7d05a5583f..25a743dc53 100644
--- a/src/iosource/PktSrc.h
+++ b/src/iosource/PktSrc.h
@@ -3,6 +3,8 @@
 #ifndef IOSOURCE_PKTSRC_PKTSRC_H
 #define IOSOURCE_PKTSRC_PKTSRC_H
 
+#include <vector>
+
 #include "IOSource.h"
 #include "BPF_Program.h"
 #include "Dict.h"
@@ -362,7 +364,7 @@ private:
 	Packet current_packet;
 
 	// For BPF filtering support.
-	PDict(BPF_Program) filters;
+	std::vector<BPF_Program *> filters;
 
 	// Only set in pseudo-realtime mode.
 	double first_timestamp;
diff --git a/src/iosource/pcap/functions.bif b/src/iosource/pcap/functions.bif
index e36c374a3c..6ba880c3b1 100644
--- a/src/iosource/pcap/functions.bif
+++ b/src/iosource/pcap/functions.bif
@@ -21,6 +21,15 @@ module Pcap;
 ##          pcap_error
 function precompile_pcap_filter%(id: PcapFilterID, s: string%): bool
 	%{
+	if ( id->AsEnum() >= 100 )
+		{
+		// We use a vector as underlying data structure for fast
+		// lookups and limit the ID space so that that doesn't grow too
+		// large.
+		builtin_error(fmt("PCAP filter ids must remain below 100 (is %ld)", id->AsInt()));
+		return new Val(false, TYPE_BOOL);
+		}
+
 	bool success = true;
 
 	const iosource::Manager::PktSrcList& pkt_srcs(iosource_mgr->GetPktSrcs());