diff --git a/mps/code/poolamc.c b/mps/code/poolamc.c
index 20c5a168cdd..82e7998a2db 100644
--- a/mps/code/poolamc.c
+++ b/mps/code/poolamc.c
@@ -113,8 +113,8 @@ static Bool amcSegCheck(amcSeg amcseg)
     CHECKD(Nailboard, amcseg->board);
     CHECKL(SegNailed(amcSeg2Seg(amcseg)) != TraceSetEMPTY);
   }
-  CHECKL(BoolCheck(amcseg->old));
-  CHECKL(BoolCheck(amcseg->deferred));
+  /* CHECKL(BoolCheck(amcseg->old)); <design/type/#bool.bitfield.check> */
+  /* CHECKL(BoolCheck(amcseg->deferred)); <design/type/#bool.bitfield.check> */
   return TRUE;
 }
 
diff --git a/mps/code/poolawl.c b/mps/code/poolawl.c
index 31af1dcd160..eb2b561eb4b 100644
--- a/mps/code/poolawl.c
+++ b/mps/code/poolawl.c
@@ -1325,7 +1325,7 @@ static Bool AWLCheck(AWL awl)
   CHECKS(AWL, awl);
   CHECKD(Pool, &awl->poolStruct);
   CHECKL(awl->poolStruct.class == AWLPoolClassGet());
-  CHECKL(AWLGrainsSize(awl, 1) == awl->poolStruct.alignment);
+  CHECKL(AWLGrainsSize(awl, (Count)1) == awl->poolStruct.alignment);
   /* Nothing to check about succAccesses. */
   CHECKL(FUNCHECK(awl->findDependent));
   /* Don't bother to check stats. */
diff --git a/mps/code/poollo.c b/mps/code/poollo.c
index af93c12bd13..c9b093c960e 100644
--- a/mps/code/poollo.c
+++ b/mps/code/poollo.c
@@ -836,7 +836,7 @@ static Bool LOCheck(LO lo)
   CHECKD(Pool, &lo->poolStruct);
   CHECKL(lo->poolStruct.class == EnsureLOPoolClass());
   CHECKL(ShiftCheck(lo->alignShift));
-  CHECKL(LOGrainsSize(lo, 1) == PoolAlignment(&lo->poolStruct));
+  CHECKL(LOGrainsSize(lo, (Count)1) == PoolAlignment(&lo->poolStruct));
   CHECKD(PoolGen, &lo->pgen);
   return TRUE;
 }
diff --git a/mps/design/type.txt b/mps/design/type.txt
index 1bf254e581d..9197c4b36ac 100644
--- a/mps/design/type.txt
+++ b/mps/design/type.txt
@@ -162,6 +162,11 @@ _`.bool.bitfield.assign`: To avoid warnings about loss of data from
 GCC with the ``-Wconversion`` option, ``misc.h`` provides the
 ``BOOLOF`` macro for coercing a value to an unsigned single-bit field.
 
+_`.bool.bitfield.check`: A Boolean bitfield cannot have an incorrect
+value, and if you call ``BoolCheck()`` on such a bitfield then GCC 4.2
+issues the warning "comparison is always true due to limited range of
+data type". When avoiding such a warning, reference this tag.
+
 
 ``typedef unsigned BufferMode``