diff --git a/ChangeLog.txt b/ChangeLog.txt
index 55907cef..5628e20a 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -27,6 +27,8 @@ Broker:
 - Miscellaneous fixes on Windows.
 - Bridge connections now default to using MQTT v3.1.1.
 - mosquitto_db_dump tool can now output some stats on clients.
+- perform utf-8 validation on incoming will, subscription and unsubscription
+  topics.
 
 Client library:
 - Outgoing messages with QoS>1 are no longer retried after a timeout period.
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index db537c90..876ae1f2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -43,6 +43,7 @@ set (MOSQ_SRCS
 	../lib/time_mosq.c
 	../lib/tls_mosq.c
 	../lib/util_mosq.c ../lib/util_mosq.h
+	../lib/utf8_mosq.c
 	websockets.c
 	../lib/will_mosq.c ../lib/will_mosq.h)
 
diff --git a/src/Makefile b/src/Makefile
index 812feaea..7dccade9 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -47,6 +47,7 @@ OBJS=	mosquitto.o \
 		sys_tree.o \
 		time_mosq.o \
 		tls_mosq.o \
+		utf8_mosq.o \
 		util_mosq.o \
 		websockets.o \
 		will_mosq.o
@@ -174,6 +175,9 @@ tls_mosq.o : ../lib/tls_mosq.c
 util_mosq.o : ../lib/util_mosq.c ../lib/util_mosq.h
 	${CROSS_COMPILE}${CC} $(BROKER_CFLAGS) -c $< -o $@
 
+utf8_mosq.o : ../lib/utf8_mosq.c
+	${CROSS_COMPILE}${CC} $(BROKER_CFLAGS) -c $< -o $@
+
 websockets.o : websockets.c mosquitto_broker.h
 	${CROSS_COMPILE}${CC} $(BROKER_CFLAGS) -c $< -o $@
 
diff --git a/src/handle_subscribe.c b/src/handle_subscribe.c
index 847553ce..13e0757b 100644
--- a/src/handle_subscribe.c
+++ b/src/handle_subscribe.c
@@ -67,19 +67,28 @@ int handle__subscribe(struct mosquitto_db *db, struct mosquitto *context)
 
 		if(sub){
 			if(STREMPTY(sub)){
-				log__printf(NULL, MOSQ_LOG_INFO, "Empty subscription string from %s, disconnecting.",
-					context->address);
+				log__printf(NULL, MOSQ_LOG_INFO,
+						"Empty subscription string from %s, disconnecting.",
+						context->address);
 				mosquitto__free(sub);
 				mosquitto__free(payload);
 				return 1;
 			}
 			if(mosquitto_sub_topic_check(sub)){
-				log__printf(NULL, MOSQ_LOG_INFO, "Invalid subscription string from %s, disconnecting.",
-					context->address);
+				log__printf(NULL, MOSQ_LOG_INFO,
+						"Invalid subscription string from %s, disconnecting.",
+						context->address);
 				mosquitto__free(sub);
 				mosquitto__free(payload);
 				return 1;
 			}
+			if(mosquitto_validate_utf8(sub, strlen(sub))){
+				log__printf(NULL, MOSQ_LOG_INFO,
+						"Malformed UTF-8 in subscription string from %s, disconnecting.",
+						context->id);
+				mosquitto__free(sub);
+				return 1;
+			}
 
 			if(packet__read_byte(&context->in_packet, &qos)){
 				mosquitto__free(sub);
@@ -87,8 +96,9 @@ int handle__subscribe(struct mosquitto_db *db, struct mosquitto *context)
 				return 1;
 			}
 			if(qos > 2){
-				log__printf(NULL, MOSQ_LOG_INFO, "Invalid QoS in subscription command from %s, disconnecting.",
-					context->address);
+				log__printf(NULL, MOSQ_LOG_INFO,
+						"Invalid QoS in subscription command from %s, disconnecting.",
+						context->address);
 				mosquitto__free(sub);
 				mosquitto__free(payload);
 				return 1;
diff --git a/src/handle_unsubscribe.c b/src/handle_unsubscribe.c
index af7a9587..45c0ea02 100644
--- a/src/handle_unsubscribe.c
+++ b/src/handle_unsubscribe.c
@@ -54,14 +54,23 @@ int handle__unsubscribe(struct mosquitto_db *db, struct mosquitto *context)
 
 		if(sub){
 			if(STREMPTY(sub)){
-				log__printf(NULL, MOSQ_LOG_INFO, "Empty unsubscription string from %s, disconnecting.",
-					context->id);
+				log__printf(NULL, MOSQ_LOG_INFO,
+						"Empty unsubscription string from %s, disconnecting.",
+						context->id);
 				mosquitto__free(sub);
 				return 1;
 			}
 			if(mosquitto_sub_topic_check(sub)){
-				log__printf(NULL, MOSQ_LOG_INFO, "Invalid unsubscription string from %s, disconnecting.",
-					context->id);
+				log__printf(NULL, MOSQ_LOG_INFO,
+						"Invalid unsubscription string from %s, disconnecting.",
+						context->id);
+				mosquitto__free(sub);
+				return 1;
+			}
+			if(mosquitto_validate_utf8(sub, strlen(sub))){
+				log__printf(NULL, MOSQ_LOG_INFO,
+						"Malformed UTF-8 in unsubscription string from %s, disconnecting.",
+						context->id);
 				mosquitto__free(sub);
 				return 1;
 			}