diff --git a/hw/char/sclpconsole-lm.c b/hw/char/sclpconsole-lm.c
index c500bda..cc4d70a 100644
--- a/hw/char/sclpconsole-lm.c
+++ b/hw/char/sclpconsole-lm.c
@@ -102,12 +102,12 @@ static bool can_handle_event(uint8_t type)
     return type == SCLP_EVENT_MESSAGE || type == SCLP_EVENT_PMSGCMD;
 }
 
-static unsigned int send_mask(void)
+static sccb_mask_t send_mask(void)
 {
     return SCLP_EVENT_MASK_OP_CMD | SCLP_EVENT_MASK_PMSGCMD;
 }
 
-static unsigned int receive_mask(void)
+static sccb_mask_t receive_mask(void)
 {
     return SCLP_EVENT_MASK_MSG | SCLP_EVENT_MASK_PMSGCMD;
 }
diff --git a/hw/char/sclpconsole.c b/hw/char/sclpconsole.c
index d0265df..ec9db13 100644
--- a/hw/char/sclpconsole.c
+++ b/hw/char/sclpconsole.c
@@ -83,12 +83,12 @@ static bool can_handle_event(uint8_t type)
     return type == SCLP_EVENT_ASCII_CONSOLE_DATA;
 }
 
-static unsigned int send_mask(void)
+static sccb_mask_t send_mask(void)
 {
     return SCLP_EVENT_MASK_MSG_ASCII;
 }
 
-static unsigned int receive_mask(void)
+static sccb_mask_t receive_mask(void)
 {
     return SCLP_EVENT_MASK_MSG_ASCII;
 }
diff --git a/hw/s390x/event-facility.c b/hw/s390x/event-facility.c
index 9233892..e04ed9f 100644
--- a/hw/s390x/event-facility.c
+++ b/hw/s390x/event-facility.c
@@ -29,8 +29,8 @@ typedef struct SCLPEventsBus {
 struct SCLPEventFacility {
     SysBusDevice parent_obj;
     SCLPEventsBus sbus;
-    /* guest' receive mask */
-    unsigned int receive_mask;
+    /* guest's receive mask */
+    sccb_mask_t receive_mask;
     /*
      * when false, we keep the same broken, backwards compatible behaviour as
      * before, allowing only masks of size exactly 4; when true, we implement
@@ -61,9 +61,9 @@ static bool event_pending(SCLPEventFacility *ef)
     return false;
 }
 
-static unsigned int get_host_send_mask(SCLPEventFacility *ef)
+static sccb_mask_t get_host_send_mask(SCLPEventFacility *ef)
 {
-    unsigned int mask;
+    sccb_mask_t mask;
     BusChild *kid;
     SCLPEventClass *child;
 
@@ -77,9 +77,9 @@ static unsigned int get_host_send_mask(SCLPEventFacility *ef)
     return mask;
 }
 
-static unsigned int get_host_receive_mask(SCLPEventFacility *ef)
+static sccb_mask_t get_host_receive_mask(SCLPEventFacility *ef)
 {
-    unsigned int mask;
+    sccb_mask_t mask;
     BusChild *kid;
     SCLPEventClass *child;
 
@@ -189,7 +189,7 @@ out:
 }
 
 static uint16_t handle_sccb_read_events(SCLPEventFacility *ef, SCCB *sccb,
-                                        unsigned int mask)
+                                        sccb_mask_t mask)
 {
     uint16_t rc;
     int slen;
@@ -242,8 +242,8 @@ static void copy_mask(uint8_t *dst, uint8_t *src, uint16_t dst_len,
 
 static void read_event_data(SCLPEventFacility *ef, SCCB *sccb)
 {
-    unsigned int sclp_active_selection_mask;
-    unsigned int sclp_cp_receive_mask;
+    sccb_mask_t sclp_active_selection_mask;
+    sccb_mask_t sclp_cp_receive_mask;
 
     ReadEventData *red = (ReadEventData *) sccb;
 
@@ -285,7 +285,7 @@ static void write_event_mask(SCLPEventFacility *ef, SCCB *sccb)
 {
     WriteEventMask *we_mask = (WriteEventMask *) sccb;
     uint16_t mask_length = be16_to_cpu(we_mask->mask_length);
-    uint32_t tmp_mask;
+    sccb_mask_t tmp_mask;
 
     if (!mask_length || (mask_length > SCLP_EVENT_MASK_LEN_MAX) ||
         ((mask_length != 4) && !ef->allow_all_mask_sizes)) {
diff --git a/hw/s390x/sclpcpu.c b/hw/s390x/sclpcpu.c
index 3ee890b..50c021b 100644
--- a/hw/s390x/sclpcpu.c
+++ b/hw/s390x/sclpcpu.c
@@ -37,12 +37,12 @@ void raise_irq_cpu_hotplug(void)
     sclp_service_interrupt(0);
 }
 
-static unsigned int send_mask(void)
+static sccb_mask_t send_mask(void)
 {
     return SCLP_EVENT_MASK_CONFIG_MGT_DATA;
 }
 
-static unsigned int receive_mask(void)
+static sccb_mask_t receive_mask(void)
 {
     return 0;
 }
diff --git a/hw/s390x/sclpquiesce.c b/hw/s390x/sclpquiesce.c
index 0241643..1c8f5c9 100644
--- a/hw/s390x/sclpquiesce.c
+++ b/hw/s390x/sclpquiesce.c
@@ -28,12 +28,12 @@ static bool can_handle_event(uint8_t type)
     return type == SCLP_EVENT_SIGNAL_QUIESCE;
 }
 
-static unsigned int send_mask(void)
+static sccb_mask_t send_mask(void)
 {
     return SCLP_EVENT_MASK_SIGNAL_QUIESCE;
 }
 
-static unsigned int receive_mask(void)
+static sccb_mask_t receive_mask(void)
 {
     return 0;
 }
diff --git a/include/hw/s390x/event-facility.h b/include/hw/s390x/event-facility.h
index 5119b9b..0e2b761 100644
--- a/include/hw/s390x/event-facility.h
+++ b/include/hw/s390x/event-facility.h
@@ -28,12 +28,14 @@
 #define SCLP_EVENT_SIGNAL_QUIESCE               0x1d
 
 /* SCLP event masks */
-#define SCLP_EVENT_MASK_SIGNAL_QUIESCE          0x00000008
-#define SCLP_EVENT_MASK_MSG_ASCII               0x00000040
-#define SCLP_EVENT_MASK_CONFIG_MGT_DATA         0x10000000
-#define SCLP_EVENT_MASK_OP_CMD                  0x80000000
-#define SCLP_EVENT_MASK_MSG                     0x40000000
-#define SCLP_EVENT_MASK_PMSGCMD                 0x00800000
+#define SCLP_EVMASK(T)  (1ULL << (sizeof(sccb_mask_t) * 8 - (T)))
+
+#define SCLP_EVENT_MASK_OP_CMD          SCLP_EVMASK(SCLP_EVENT_OPRTNS_COMMAND)
+#define SCLP_EVENT_MASK_MSG             SCLP_EVMASK(SCLP_EVENT_MESSAGE)
+#define SCLP_EVENT_MASK_CONFIG_MGT_DATA SCLP_EVMASK(SCLP_EVENT_CONFIG_MGT_DATA)
+#define SCLP_EVENT_MASK_PMSGCMD         SCLP_EVMASK(SCLP_EVENT_PMSGCMD)
+#define SCLP_EVENT_MASK_MSG_ASCII       SCLP_EVMASK(SCLP_EVENT_ASCII_CONSOLE_DATA)
+#define SCLP_EVENT_MASK_SIGNAL_QUIESCE  SCLP_EVMASK(SCLP_EVENT_SIGNAL_QUIESCE)
 
 #define SCLP_UNCONDITIONAL_READ                 0x00
 #define SCLP_SELECTIVE_READ                     0x01
@@ -71,6 +73,8 @@ typedef struct WriteEventMask {
 #define WEM_RECEIVE_MASK(wem, mask_len) ((wem)->masks + 2 * (mask_len))
 #define WEM_SEND_MASK(wem, mask_len) ((wem)->masks + 3 * (mask_len))
 
+typedef uint32_t sccb_mask_t;
+
 typedef struct EventBufferHeader {
     uint16_t length;
     uint8_t  type;
@@ -160,7 +164,7 @@ typedef struct WriteEventData {
 typedef struct ReadEventData {
     SCCBHeader h;
     union {
-        uint32_t mask;
+        sccb_mask_t mask;
         EventBufferHeader ebh;
     };
 } QEMU_PACKED ReadEventData;
@@ -177,10 +181,10 @@ typedef struct SCLPEventClass {
     int (*exit)(SCLPEvent *event);
 
     /* get SCLP's send mask */
-    unsigned int (*get_send_mask)(void);
+    sccb_mask_t (*get_send_mask)(void);
 
     /* get SCLP's receive mask */
-    unsigned int (*get_receive_mask)(void);
+    sccb_mask_t (*get_receive_mask)(void);
 
     int (*read_event_data)(SCLPEvent *event, EventBufferHeader *evt_buf_hdr,
                            int *slen);
