diff --git a/include/minix/com.h b/include/minix/com.h
index ef8dc8f04..47e781c85 100755
--- a/include/minix/com.h
+++ b/include/minix/com.h
@@ -9,8 +9,10 @@
 #define ANY		0x7ace	/* used to indicate 'any process' */
 #define NONE 		0x6ace  /* used to indicate 'no process at all' */
 #define SELF		0x8ace 	/* used to indicate 'own process' */
-#define _MAX_MAGIC_PROC (SELF)	/* used by <minix/endpoint.h> 
-				   to determine generation size */
+/* check if the magic process numbers are valid process table slot numbers */
+#if (ANY < NR_PROCS)
+#error "Magic process number in the process table range"
+#endif
 
 /*===========================================================================*
  *            	Process numbers of processes in the system image	     *
diff --git a/include/minix/endpoint.h b/include/minix/endpoint.h
index 97a778763..105a58b4d 100644
--- a/include/minix/endpoint.h
+++ b/include/minix/endpoint.h
@@ -15,12 +15,14 @@
  * the generation size is big enough to start the next generation
  * above the highest magic number.
  */
-#define _ENDPOINT_GENERATION_SIZE (NR_TASKS+_MAX_MAGIC_PROC+1)
-#define _ENDPOINT_MAX_GENERATION  (INT_MAX/_ENDPOINT_GENERATION_SIZE-1)
+#define _ENDPOINT_GENERATION_BITS	16
+#define _ENDPOINT_PNUM_BITS		16
+#define _ENDPOINT_MAX_GENERATION	((1 << _ENDPOINT_GENERATION_BITS)-1)
+#define _ENDPOINT_MAX_PNUM		((1 << _ENDPOINT_PNUM_BITS) - 1)
 
 /* Generation + Process slot number <-> endpoint. */
-#define _ENDPOINT(g, p) ((g) * _ENDPOINT_GENERATION_SIZE + (p))
-#define _ENDPOINT_G(e) (((e)+NR_TASKS) / _ENDPOINT_GENERATION_SIZE)
-#define _ENDPOINT_P(e) ((((e)+NR_TASKS) % _ENDPOINT_GENERATION_SIZE) - NR_TASKS)
+#define _ENDPOINT(g, p)	((endpoint_t)(((g) << _ENDPOINT_PNUM_BITS) | (p)))
+#define _ENDPOINT_G(e) 	((u16_t)((e) >> _ENDPOINT_PNUM_BITS))
+#define _ENDPOINT_P(e) 	((i16_t)((e) & _ENDPOINT_MAX_PNUM))
 
 #endif