diff --git a/mps/code/event.c b/mps/code/event.c
index d4b32f83a2c..0b4d16353b4 100644
--- a/mps/code/event.c
+++ b/mps/code/event.c
@@ -46,11 +46,15 @@ Word EventKindControl; /* Bit set used to control output. */
 Res EventFlush(void)
 {
   Res res;
+  size_t size;
  
   AVER(eventInited);
 
-  res = (Res)mps_io_write(eventIO, (void *)eventBuffer,
-                          EventNext - eventBuffer);
+  AVER(eventBuffer <= EventNext);
+  AVER(EventNext <= eventBuffer + EventBufferSIZE);
+  size = (size_t)(EventNext - eventBuffer);
+
+  res = (Res)mps_io_write(eventIO, (void *)eventBuffer, size);
   EventNext = eventBuffer;
   if (res != ResOK) return res;
 
diff --git a/mps/code/event.h b/mps/code/event.h
index 139460955fa..97e622b628d 100644
--- a/mps/code/event.h
+++ b/mps/code/event.h
@@ -35,43 +35,8 @@ extern void EventLabelAddr(Addr, Word);
 extern Res EventFlush(void);
 
 
-/* Event Kinds --- see <design/telemetry/>
- *
- * All events are classified as being of one event type.
- * They are small enough to be able to be used as shifts within a word.
- */
-
-#define EventKindArena      ((EventKind)0) /* Per space or arena */
-#define EventKindPool       ((EventKind)1) /* Per pool */
-#define EventKindTrace      ((EventKind)2) /* Per trace or scan */
-#define EventKindSeg        ((EventKind)3) /* Per seg */
-#define EventKindRef        ((EventKind)4) /* Per ref or fix */
-#define EventKindObject     ((EventKind)5) /* Per alloc or object */
-#define EventKindUser       ((EventKind)6) /* User-invoked */
-
-#define EventKindNumber     ((Count)7) /* Number of event kinds */
-
-
-/* Event type definitions
- *
- * Define various constants for each event type to describe them.
- */
-
-/* Note that enum values can be up to fifteen bits long portably. */
-#define EVENT_ENUM(X, type, code, always, kind, count, format) \
-  enum { \
-    Event##type##High = ((code >> 8) & 0xFF), \
-    Event##type##Low = (code & 0xFF), \
-    Event##type##Always = always, \
-    Event##type##Kind = EventKind##kind \
-  };
-
-EVENT_LIST(EVENT_ENUM, X)
-
-
 /* Event writing support */
 
-/* extern EventUnion EventMould; */
 extern char *EventNext, *EventLimit;
 extern Word EventKindControl;
 
diff --git a/mps/code/eventcom.h b/mps/code/eventcom.h
index 7d372cdd47a..18bef8ec4ca 100644
--- a/mps/code/eventcom.h
+++ b/mps/code/eventcom.h
@@ -16,8 +16,8 @@
 /* Types for event fields */
 
 typedef Word EventType;
-typedef size_t EventCode;
-typedef Index EventKind;
+typedef unsigned short EventCode;
+typedef unsigned EventKind;
 
 typedef Byte EventStringLen;
 
@@ -33,6 +33,39 @@ typedef EventStringStruct *EventString;
 #define EventCodeMAX ((EventCode)0x0069)
 
 
+/* Event Kinds --- see <design/telemetry/>
+ *
+ * All events are classified as being of one event type.
+ * They are small enough to be able to be used as shifts within a word.
+ */
+
+enum {
+  EventKindArena,       /* Per space or arena */
+  EventKindPool,        /* Per pool */
+  EventKindTrace,       /* Per trace or scan */
+  EventKindSeg,         /* Per seg */
+  EventKindRef,         /* Per ref or fix */
+  EventKindObject,      /* Per alloc or object */
+  EventKindUser,        /* User-invoked */
+  EventKindLIMIT
+};
+
+
+/* Event type definitions
+ *
+ * Define various constants for each event type to describe them.
+ */
+
+/* Note that enum values can be up to fifteen bits long portably. */
+#define EVENT_ENUM(X, name, code, always, kind, count, format) \
+  enum { \
+    Event##name##Always = always, \
+    Event##name##Kind = EventKind##kind \
+  };
+
+EVENT_LIST(EVENT_ENUM, X)
+
+
 /* Event*Struct -- Event Structures
  *
  * Declare the structures that are used to encode events in the internal event
@@ -112,11 +145,11 @@ typedef union EventUnion {
   BEGIN \
     size_t _string_len = (length); \
     size_t size; \
-    AVER(_string_len < EventStringLengthMAX); \
     size = offsetof(Event##name##Struct, f1.str) + _string_len; \
     EVENT_BEGIN(name, size) \
       _event->f0 = (p0); \
-      _event->f1.len = _string_len; \
+      AVER(_string_len < EventStringLengthMAX); \
+      _event->f1.len = (EventStringLen)_string_len; \
       mps_lib_memcpy(_event->f1.str, (string), _string_len); \
     EVENT_END(name, size); \
   END
@@ -141,7 +174,6 @@ typedef union EventUnion {
 #define EVENT14(name, p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13) EVENT_BEGIN(name, sizeof(Event##name##Struct)) _event->f0 = (p0); _event->f1 = (p1); _event->f2 = (p2); _event->f3 = (p3); _event->f4 = (p4); _event->f5 = (p5); _event->f6 = (p6); _event->f7 = (p7); _event->f8 = (p8); _event->f9 = (p9); _event->f10 = (p10); _event->f11 = (p11); _event->f12 = (p12); _event->f13 = (p13); EVENT_END(name, sizeof(Event##name##Struct))
 
 
-
 #define EVENT0_FIELD_PTR(name, event, i) NULL
 
 /*
diff --git a/mps/code/eventpro.c b/mps/code/eventpro.c
index 07faea3226e..e66c76a69a9 100644
--- a/mps/code/eventpro.c
+++ b/mps/code/eventpro.c
@@ -72,7 +72,7 @@ struct EventProcStruct {
 typedef struct {
   EventType type;
   char *name;
-  size_t code;
+  EventCode code;
   size_t length;
   char *format;
 } eventRecord;