diff --git a/src/Discard.cc b/src/Discard.cc
index 2705aa55be..a71b810601 100644
--- a/src/Discard.cc
+++ b/src/Discard.cc
@@ -42,7 +42,17 @@ int Discarder::NextPacket(const IP_Hdr* ip, int len, int caplen)
 		{
 		val_list* args = new val_list;
 		args->append(BuildHeader(ip4));
-		discard_packet = check_ip->Call(args)->AsBool();
+
+		try
+			{
+			discard_packet = check_ip->Call(args)->AsBool();
+			}
+
+		catch ( InterpreterException& e )
+			{
+			discard_packet = false;
+			}
+
 		delete args;
 
 		if ( discard_packet )
@@ -90,7 +100,17 @@ int Discarder::NextPacket(const IP_Hdr* ip, int len, int caplen)
 			args->append(BuildHeader(ip4));
 			args->append(BuildHeader(tp, len));
 			args->append(BuildData(data, th_len, len, caplen));
-			discard_packet = check_tcp->Call(args)->AsBool();
+
+			try
+				{
+				discard_packet = check_tcp->Call(args)->AsBool();
+				}
+
+			catch ( InterpreterException& e )
+				{
+				discard_packet = false;
+				}
+
 			delete args;
 			}
 		}
@@ -106,7 +126,17 @@ int Discarder::NextPacket(const IP_Hdr* ip, int len, int caplen)
 			args->append(BuildHeader(ip4));
 			args->append(BuildHeader(up));
 			args->append(BuildData(data, uh_len, len, caplen));
-			discard_packet = check_udp->Call(args)->AsBool();
+
+			try
+				{
+				discard_packet = check_udp->Call(args)->AsBool();
+				}
+
+			catch ( InterpreterException& e )
+				{
+				discard_packet = false;
+				}
+
 			delete args;
 			}
 		}
@@ -120,7 +150,17 @@ int Discarder::NextPacket(const IP_Hdr* ip, int len, int caplen)
 			val_list* args = new val_list;
 			args->append(BuildHeader(ip4));
 			args->append(BuildHeader(ih));
-			discard_packet = check_icmp->Call(args)->AsBool();
+
+			try
+				{
+				discard_packet = check_icmp->Call(args)->AsBool();
+				}
+
+			catch ( InterpreterException& e )
+				{
+				discard_packet = false;
+				}
+
 			delete args;
 			}
 		}
diff --git a/src/Event.h b/src/Event.h
index 805396a488..1740372407 100644
--- a/src/Event.h
+++ b/src/Event.h
@@ -41,7 +41,16 @@ protected:
 		if ( handler->ErrorHandler() )
 			reporter->BeginErrorHandler();
 
-		handler->Call(args, no_remote);
+		try
+			{
+			handler->Call(args, no_remote);
+			}
+			
+		catch ( InterpreterException& e )
+			{
+			// Already reported.
+			}
+
 		if ( obj )
 			// obj->EventDone();
 			Unref(obj);
diff --git a/src/EventHandler.cc b/src/EventHandler.cc
index 55f9902079..2867b63437 100644
--- a/src/EventHandler.cc
+++ b/src/EventHandler.cc
@@ -68,6 +68,7 @@ void EventHandler::Call(val_list* vl, bool no_remote)
 		}
 
 	if ( local )
+		// No try/catch here; we pass exceptions upstream.
 		Unref(local->Call(vl));
 	else
 		{
diff --git a/src/Expr.cc b/src/Expr.cc
index 9fecab4019..f6d1fc568e 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -3118,8 +3118,9 @@ Val* FieldExpr::Fold(Val* v) const
 		return def_attr->AttrExpr()->Eval(0);
 	else
 		{
-		Internal("field value missing");
-		return 0;
+		reporter->ExprRuntimeError(this, "field value missing");
+		assert(false);
+		return 0; // Will never get here, but compiler can't tell.
 		}
 	}
 
@@ -3730,6 +3731,7 @@ Val* RecordMatchExpr::Fold(Val* v1, Val* v2) const
 				}
 			}
 
+		// No try/catch here; we pass exceptions upstream.
 		Val* pred_val =
 			match_rec->Lookup(pred_field_index)->AsFunc()->Call(&args);
 		bool is_zero = pred_val->IsZero();
@@ -4220,7 +4222,7 @@ Val* FlattenExpr::Fold(Val* v) const
 			l->Append(fa->AttrExpr()->Eval(0));
 
 		else
-			Internal("missing field value");
+			reporter->ExprRuntimeError(this, "missing field value");
 		}
 
 	return l;
@@ -4646,7 +4648,7 @@ Val* CallExpr::Eval(Frame* f) const
 
 		if ( f )
 			f->SetCall(this);
-		ret = func->Call(v, f);
+		ret = func->Call(v, f); // No try/catch here; we pass exceptions upstream.
 		if ( f )
 			f->ClearCall();
 		// Don't Unref() the arguments, as Func::Call already did that.
diff --git a/src/LogMgr.cc b/src/LogMgr.cc
index 3f088fd439..473f480ada 100644
--- a/src/LogMgr.cc
+++ b/src/LogMgr.cc
@@ -888,9 +888,18 @@ bool LogMgr::Write(EnumVal* id, RecordVal* columns)
 			// to log this record.
 			val_list vl(1);
 			vl.append(columns->Ref());
-			Val* v = filter->pred->Call(&vl);
-			int result = v->AsBool();
-			Unref(v);
+
+			int result = 1;
+
+			try
+				{
+				Val* v = filter->pred->Call(&vl);
+				int result = v->AsBool();
+				Unref(v);
+				}
+
+			catch ( InterpreterException& e )
+				{ /* Already reported. */ }
 
 			if ( ! result )
 				continue;
@@ -920,7 +929,17 @@ bool LogMgr::Write(EnumVal* id, RecordVal* columns)
 
 			vl.append(rec_arg);
 
-			Val* v = filter->path_func->Call(&vl);
+			Val* v = 0;
+
+			try
+				{
+				v = filter->path_func->Call(&vl);
+				}
+
+			catch ( InterpreterException& e )
+				{
+				return false;
+				}
 
 			if ( ! v->Type()->Tag() == TYPE_STRING )
 				{
@@ -1569,9 +1588,19 @@ bool LogMgr::FinishedRotation(LogWriter* writer, string new_name, string old_nam
 	// Call the postprocessor function.
 	val_list vl(1);
 	vl.append(info);
-	Val* v = func->Call(&vl);
-	int result = v->AsBool();
-	Unref(v);
+
+	int result = 0;
+
+	try
+		{
+		Val* v = func->Call(&vl);
+		result = v->AsBool();
+		Unref(v);
+		}
+
+	catch ( InterpreterException& e )
+		{ /* Already reported. */ }
+
 	return result;
 	}
 
diff --git a/src/PersistenceSerializer.cc b/src/PersistenceSerializer.cc
index c72f59c0dd..c757467f90 100644
--- a/src/PersistenceSerializer.cc
+++ b/src/PersistenceSerializer.cc
@@ -200,7 +200,13 @@ void PersistenceSerializer::GotEvent(const char* name, double time,
 void PersistenceSerializer::GotFunctionCall(const char* name, double time,
 					Func* func, val_list* args)
 	{
-	func->Call(args);
+	try
+		{
+		func->Call(args);
+		}
+
+	catch ( InterpreterException& e )
+		{ /* Already reported. */ }
 	}
 
 void PersistenceSerializer::GotStateAccess(StateAccess* s)
diff --git a/src/RemoteSerializer.cc b/src/RemoteSerializer.cc
index e359a4a749..79268946d5 100644
--- a/src/RemoteSerializer.cc
+++ b/src/RemoteSerializer.cc
@@ -2809,7 +2809,13 @@ void RemoteSerializer::GotFunctionCall(const char* name, double time,
 		return;
 		}
 
-	function->Call(args);
+	try
+		{
+		function->Call(args);
+		}
+
+	catch ( InterpreterException& e )
+		{ /* Already reported. */ }
 	}
 
 void RemoteSerializer::GotID(ID* id, Val* val)
diff --git a/src/Reporter.cc b/src/Reporter.cc
index b2bffd3432..fca9a6a233 100644
--- a/src/Reporter.cc
+++ b/src/Reporter.cc
@@ -39,7 +39,7 @@ void Reporter::Info(const char* fmt, ...)
 	{
 	va_list ap;
 	va_start(ap, fmt);
-	DoLog("", reporter_info, stderr, 0, 0, true, true, fmt, ap);
+	DoLog("", reporter_info, stderr, 0, 0, true, true, 0, fmt, ap);
 	va_end(ap);
 	}
 
@@ -47,7 +47,7 @@ void Reporter::Warning(const char* fmt, ...)
 	{
 	va_list ap;
 	va_start(ap, fmt);
-	DoLog("warning", reporter_warning, stderr, 0, 0, true, true, fmt, ap);
+	DoLog("warning", reporter_warning, stderr, 0, 0, true, true, 0, fmt, ap);
 	va_end(ap);
 	}
 
@@ -56,7 +56,7 @@ void Reporter::Error(const char* fmt, ...)
 	++errors;
 	va_list ap;
 	va_start(ap, fmt);
-	DoLog("error", reporter_error, stderr, 0, 0, true, true, fmt, ap);
+	DoLog("error", reporter_error, stderr, 0, 0, true, true, 0, fmt, ap);
 	va_end(ap);
 	}
 
@@ -66,7 +66,7 @@ void Reporter::FatalError(const char* fmt, ...)
 	va_start(ap, fmt);
 
 	// Always log to stderr.
-	DoLog("fatal error", 0, stderr, 0, 0, true, false, fmt, ap);
+	DoLog("fatal error", 0, stderr, 0, 0, true, false, 0, fmt, ap);
 
 	va_end(ap);
 
@@ -80,7 +80,7 @@ void Reporter::FatalErrorWithCore(const char* fmt, ...)
 	va_start(ap, fmt);
 
 	// Always log to stderr.
-	DoLog("fatal error", 0, stderr, 0, 0, true, false, fmt, ap);
+	DoLog("fatal error", 0, stderr, 0, 0, true, false, 0, fmt, ap);
 
 	va_end(ap);
 
@@ -88,13 +88,29 @@ void Reporter::FatalErrorWithCore(const char* fmt, ...)
 	abort();
 	}
 
+void Reporter::ExprRuntimeError(const Expr* expr, const char* fmt, ...)
+	{
+	++errors;
+
+	ODesc d;
+	expr->Describe(&d);
+
+	PushLocation(expr->GetLocationInfo());
+	va_list ap;
+	va_start(ap, fmt);
+	DoLog("expression error", reporter_error, stderr, 0, 0, true, true, d.Description(), fmt, ap);
+	va_end(ap);
+	PopLocation();
+	throw InterpreterException();
+	}
+
 void Reporter::InternalError(const char* fmt, ...)
 	{
 	va_list ap;
 	va_start(ap, fmt);
 
 	// Always log to stderr.
-	DoLog("internal error", 0, stderr, 0, 0, true, false, fmt, ap);
+	DoLog("internal error", 0, stderr, 0, 0, true, false, 0, fmt, ap);
 
 	va_end(ap);
 
@@ -106,7 +122,7 @@ void Reporter::InternalWarning(const char* fmt, ...)
 	{
 	va_list ap;
 	va_start(ap, fmt);
-	DoLog("internal warning", reporter_warning, stderr, 0, 0, true, true, fmt, ap);
+	DoLog("internal warning", reporter_warning, stderr, 0, 0, true, true, 0, fmt, ap);
 	va_end(ap);
 	}
 
@@ -133,7 +149,7 @@ void Reporter::WeirdHelper(EventHandlerPtr event, Val* conn_val, const char* add
 
 	va_list ap;
 	va_start(ap, fmt_name);
-	DoLog("weird", event, stderr, 0, vl, false, false, fmt_name, ap);
+	DoLog("weird", event, stderr, 0, vl, false, false, 0, fmt_name, ap);
 	va_end(ap);
 
 	delete vl;
@@ -147,7 +163,7 @@ void Reporter::WeirdFlowHelper(const uint32* orig, const uint32* resp, const cha
 
 	va_list ap;
 	va_start(ap, fmt_name);
-	DoLog("weird", flow_weird, stderr, 0, vl, false, false, fmt_name, ap);
+	DoLog("weird", flow_weird, stderr, 0, vl, false, false, 0, fmt_name, ap);
 	va_end(ap);
 
 	delete vl;
@@ -173,7 +189,7 @@ void Reporter::Weird(const uint32* orig, const uint32* resp, const char* name)
 	WeirdFlowHelper(orig, resp, "%s", name);
 	}
 
-void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Connection* conn, val_list* addl, bool location, bool time, const char* fmt, va_list ap)
+void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Connection* conn, val_list* addl, bool location, bool time, const char* postfix, const char* fmt, va_list ap)
 	{
 	static char tmp[512];
 
@@ -235,6 +251,9 @@ void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Conne
 		int n = vsnprintf(buffer, size, fmt, aq);
 		va_end(aq);
 
+		if ( postfix )
+			n += strlen(postfix) + 10; // Add a bit of slack.
+
 		if ( n > -1 && n < size )
 			// We had enough space;
 			break;
@@ -247,6 +266,11 @@ void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Conne
 			FatalError("out of memory in Reporter");
 		}
 
+	if ( postfix )
+		// Note, if you change this fmt string, adjust the additional
+		// buffer size above.
+		sprintf(buffer + strlen(buffer), " [%s]", postfix);
+
 	if ( event && via_events && ! in_error_handler )
 		{
 		val_list* vl = new val_list;
diff --git a/src/Reporter.h b/src/Reporter.h
index d0fc66299b..52a2aff53a 100644
--- a/src/Reporter.h
+++ b/src/Reporter.h
@@ -14,6 +14,22 @@
 
 class Connection;
 class Location;
+class Reporter;
+
+// One cannot raise this exception directly, go through the
+// Reporter's methods instead.
+
+class ReporterException {
+protected:
+	friend class Reporter;
+	ReporterException()	{}
+};
+
+class InterpreterException : public ReporterException {
+protected:
+	friend class Reporter;
+	InterpreterException()	{}
+};
 
 class Reporter {
 public:
@@ -42,6 +58,10 @@ public:
 	// reported and always generate a core dump.
 	void FatalErrorWithCore(const char* fmt, ...);
 
+	// Report a runtime error in evaluating a Bro script expression. This
+	// function will not return but raise an InterpreterException.
+	void ExprRuntimeError(const Expr* expr, const char* fmt, ...);
+
 	// Report a traffic weirdness, i.e., an unexpected protocol situation
 	// that may lead to incorrectly processing a connnection.
 	void Weird(const char* name);	// Raises net_weird().
@@ -87,7 +107,9 @@ public:
 	void EndErrorHandler()	{ --in_error_handler; }
 
 private:
-	void DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Connection* conn, val_list* addl, bool location, bool time, const char* fmt, va_list ap);
+	void DoLog(const char* prefix, EventHandlerPtr event, FILE* out,
+		   Connection* conn, val_list* addl, bool location, bool time,
+		   const char* postfix, const char* fmt, va_list ap);
 
 	// The order if addl, name needs to be like that since fmt_name can
 	// contain format specifiers
diff --git a/src/RuleCondition.cc b/src/RuleCondition.cc
index 1b94fcffe6..8852747cc4 100644
--- a/src/RuleCondition.cc
+++ b/src/RuleCondition.cc
@@ -149,9 +149,19 @@ bool RuleConditionEval::DoMatch(Rule* rule, RuleEndpointState* state,
 	else
 		args.append(new StringVal(""));
 
-	Val* val = id->ID_Val()->AsFunc()->Call(&args);
-	bool result = val->AsBool();
-	Unref(val);
+	bool result = 0;
+
+	try
+		{
+		Val* val = id->ID_Val()->AsFunc()->Call(&args);
+		result = val->AsBool();
+		Unref(val);
+		}
+
+	catch ( InterpreterException& e )
+		{
+		result = false;
+		}
 
 	return result;
 	}
diff --git a/src/Sessions.cc b/src/Sessions.cc
index 1d2604b8db..572e8dea59 100644
--- a/src/Sessions.cc
+++ b/src/Sessions.cc
@@ -331,7 +331,14 @@ void NetSessions::NextPacketSecondary(double /* t */, const struct pcap_pkthdr*
 			args->append(cmd_val);
 			args->append(BuildHeader(ip));
 			// ### Need to queue event here.
-			sp->Event()->Event()->Call(args);
+			try
+				{
+				sp->Event()->Event()->Call(args);
+				}
+
+			catch ( InterpreterException& e )
+				{ /* Already reported. */ }
+
 			delete args;
 			}
 		}
diff --git a/src/Val.cc b/src/Val.cc
index 164994b3b8..ddf04bb528 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -2007,7 +2007,16 @@ Val* TableVal::Default(Val* index)
 	else
 		vl->append(index->Ref());
 
-	Val* result = f->Call(vl);
+	Val* result = 0;
+
+	try
+		{
+		result = f->Call(vl);
+		}
+		
+	catch ( InterpreterException& e )
+		{ /* Already reported. */ }
+
 	delete vl;
 
 	if ( ! result )
@@ -2466,10 +2475,20 @@ double TableVal::CallExpireFunc(Val* idx)
 
 	vl->append(idx);
 
-	Val* vs = expire_expr->Eval(0)->AsFunc()->Call(vl);
-	double secs = vs->AsInterval();
-	Unref(vs);
-	delete vl;
+	double secs;
+
+	try
+		{
+		Val* vs = expire_expr->Eval(0)->AsFunc()->Call(vl);
+		secs = vs->AsInterval();
+		Unref(vs);
+		delete vl;
+		}
+
+	catch ( InterpreterException& e )
+		{
+		secs = 0;
+		}
 
 	return secs;
 	}