diff --git a/src/zm_monitor.cpp b/src/zm_monitor.cpp
index 53894f782..d5590333b 100644
--- a/src/zm_monitor.cpp
+++ b/src/zm_monitor.cpp
@@ -111,9 +111,14 @@ Monitor::~Monitor()
 		shared_data->state = state = IDLE;
 		shared_data->last_read_index = image_buffer_count;
 	}
+	else if ( purpose == CAPTURE )
+	{
+		shared_data->valid = false;
+		memset( shm_ptr, 0, shm_size );
+	}
 
 	struct shmid_ds shm_data;
-	if ( shmctl( shmid, IPC_STAT, &shm_data ) )
+	if ( shmctl( shm_id, IPC_STAT, &shm_data ) )
 	{
 		Error(( "Can't shmctl: %s", strerror(errno)));
 		exit( -1 );
@@ -121,7 +126,7 @@ Monitor::~Monitor()
 
 	if ( shm_data.shm_nattch <= 1 )
 	{
-		if ( shmctl( shmid, IPC_RMID, 0 ) )
+		if ( shmctl( shm_id, IPC_RMID, 0 ) )
 		{
 			Error(( "Can't shmctl: %s", strerror(errno)));
 			exit( -1 );
@@ -148,19 +153,19 @@ void Monitor::Setup()
 
 	Debug( 1, ( "monitor purpose=%d", purpose ));
 
-	int shared_data_size = sizeof(SharedData)
-						 + sizeof(TriggerData)
-						 + (image_buffer_count*sizeof(struct timeval))
-						 + (image_buffer_count*camera->ImageSize());
+	shm_size = sizeof(SharedData)
+			 + sizeof(TriggerData)
+			 + (image_buffer_count*sizeof(struct timeval))
+			 + (image_buffer_count*camera->ImageSize());
 
-	Debug( 1, ( "shm.size=%d", shared_data_size ));
-	shmid = shmget( (config.shm_key&0xffffff00)|id, shared_data_size, IPC_CREAT|0700 );
-	if ( shmid < 0 )
+	Debug( 1, ( "shm.size=%d", shm_size ));
+	shm_id = shmget( (config.shm_key&0xffffff00)|id, shm_size, IPC_CREAT|0700 );
+	if ( shm_id < 0 )
 	{
 		Error(( "Can't shmget, probably not enough shared memory space free: %s", strerror(errno)));
 		exit( -1 );
 	}
-	unsigned char *shm_ptr = (unsigned char *)shmat( shmid, 0, 0 );
+	shm_ptr = (unsigned char *)shmat( shm_id, 0, 0 );
 	if ( shm_ptr < 0 )
 	{
 		Error(( "Can't shmat: %s", strerror(errno)));
@@ -174,7 +179,7 @@ void Monitor::Setup()
 
 	if ( purpose == CAPTURE )
 	{
-		memset( shared_data, 0, shared_data_size );
+		memset( shm_ptr, 0, shm_size );
 		shared_data->size = sizeof(SharedData);
 		shared_data->valid = true;
 		shared_data->active = enabled;
diff --git a/src/zm_monitor.h b/src/zm_monitor.h
index 88c9bf065..77a67f927 100644
--- a/src/zm_monitor.h
+++ b/src/zm_monitor.h
@@ -72,6 +72,46 @@ public:
 		TAPE
 	} State;
 
+protected:
+	typedef enum { GET_SETTINGS=0x1, SET_SETTINGS=0x2, RELOAD=0x4, SUSPEND=0x10, RESUME=0x20 } Action;
+
+	typedef struct
+	{
+		int size;
+		bool valid;
+		bool active;
+		bool signal;
+		State state;
+		int last_write_index;
+		int last_read_index;
+		time_t last_image_time;
+		int last_event;
+		int action;
+		int brightness;
+		int hue;
+		int colour;
+		int contrast;
+		int alarm_x;
+		int alarm_y;
+	} SharedData;
+
+	typedef enum { TRIGGER_CANCEL, TRIGGER_ON, TRIGGER_OFF } TriggerState;
+	typedef struct
+	{
+		int size;
+		TriggerState trigger_state;
+		int trigger_score;
+		char trigger_cause[32];
+		char trigger_text[256];
+		char trigger_showtext[32];
+	} TriggerData;
+
+	typedef struct Snapshot
+	{
+		struct timeval	*timestamp;
+		Image	*image;
+	};
+
 protected:
 	// These are read from the DB and thereafter remain unchanged
 	int				id;
@@ -119,52 +159,17 @@ protected:
 	time_t			start_time;
 	time_t			last_fps_time;
 	time_t			auto_resume_time;
-	int				shmid;
 
-	typedef struct Snapshot
-	{
-		struct timeval	*timestamp;
-		Image	*image;
-	};
+	int				shm_id;
+	int				shm_size;
+	unsigned char	*shm_ptr;
 
-	Snapshot *image_buffer;
+	SharedData		*shared_data;
+	TriggerData		*trigger_data;
 
-	typedef enum { GET_SETTINGS=0x1, SET_SETTINGS=0x2, RELOAD=0x4, SUSPEND=0x10, RESUME=0x20 } Action;
-	typedef struct
-	{
-		int size;
-		bool valid;
-		bool active;
-		bool signal;
-		State state;
-		int last_write_index;
-		int last_read_index;
-		time_t last_image_time;
-		int last_event;
-		int action;
-		int brightness;
-		int hue;
-		int colour;
-		int contrast;
-		int alarm_x;
-		int alarm_y;
-	} SharedData;
+	Snapshot		*image_buffer;
 
-	typedef enum { TRIGGER_CANCEL, TRIGGER_ON, TRIGGER_OFF } TriggerState;
-	typedef struct
-	{
-		int size;
-		TriggerState trigger_state;
-		int trigger_score;
-		char trigger_cause[32];
-		char trigger_text[256];
-		char trigger_showtext[32];
-	} TriggerData;
-
-	SharedData *shared_data;
-	TriggerData *trigger_data;
-
-	Camera *camera;
+	Camera			*camera;
 
 public:
 	Monitor( int p_id, char *p_name, int p_function, bool p_enabled, Camera *p_camera, int p_orientation, char *p_event_prefix, char *p_label_format, const Coord &p_label_coord, int p_image_buffer_count, int p_warmup_count, int p_pre_event_count, int p_post_event_count, int p_alarm_frame_count, int p_section_length, int p_frame_skip, int p_capture_delay, int p_fps_report_interval, int p_ref_blend_perc, bool p_track_motion, Purpose p_purpose=QUERY, int p_n_zones=0, Zone *p_zones[]=0 );