diff --git a/TO_DO b/TO_DO
index 6fad4d76d..7aaa86a58 100644
--- a/TO_DO
+++ b/TO_DO
@@ -13,14 +13,13 @@ STK:
 - inline c_interface functions (static #included?)
 - look for a system regexp library before using the one in Yap.
 - see why tag2.pl is not compiling.
-- readline is installed on thor, but is not "found" by configure and
-  is not working when manually forced in. (missing symbols, maybe because
-  there is no libtermcap.a?)
 - make docs/Makefile configurable.
 - break up yap.tex.
 - start devel.tex.
 - should sigactions be executed when Yap is waiting at the prompt?
 - see if on_signal/3 works through the C interface as well.
+- see how MPI libraries interact with YAP's signal handling.
+- make the MPI interface able to pass infinite terms to MPI_Send().
 
 
 TO CHECK:
diff --git a/config.h.in b/config.h.in
index 37c28a69c..23d1a3a7b 100644
--- a/config.h.in
+++ b/config.h.in
@@ -111,25 +111,22 @@
 #undef MinStackSpace
 #undef  MinHeapSpace
 
-#undef UsrTrailSpace
-#undef UsrStackSpace
-#undef  UsrHeapSpace
+#undef DefTrailSpace
+#undef DefStackSpace
+#undef  DefHeapSpace
 
-#if (UsrTrailSpace > MinTrailSpace)
-  #define DefTrailSpace	UsrTrailSpace
-#else
+#if (DefTrailSpace < MinTrailSpace)
+  #undef DefTrailSpace
   #define DefTrailSpace	MinTrailSpace
 #endif
 
-#if (UsrStackSpace > MinStackSpace)
-  #define DefStackSpace	UsrStackSpace
-#else
+#if (DefStackSpace < MinStackSpace)
+  #undef DefStackSpace
   #define DefStackSpace	MinStackSpace
 #endif
 
-#if (UsrHeapSpace > MinHeapSpace)
-  #define DefHeapSpace	UsrHeapSpace
-#else
+#if (DefHeapSpace < MinHeapSpace)
+  #undef DefHeapSpace
   #define DefHeapSpace	MinHeapSpace
 #endif
 
diff --git a/configure.in b/configure.in
index 498cb7dae..0594d2f07 100644
--- a/configure.in
+++ b/configure.in
@@ -126,9 +126,9 @@ else
 	AC_DEFINE(MinTrailSpace,( 32*SIZEOF_INT_P))
 fi
 
-eval "AC_DEFINE(UsrHeapSpace,($yap_cv_heap_space))"
-eval "AC_DEFINE(UsrStackSpace,($yap_cv_stack_space))"
-eval "AC_DEFINE(UsrTrailSpace,($yap_cv_trail_space))"
+eval "AC_DEFINE(DefHeapSpace,($yap_cv_heap_space))"
+eval "AC_DEFINE(DefStackSpace,($yap_cv_stack_space))"
+eval "AC_DEFINE(DefTrailSpace,($yap_cv_trail_space))"
 
 AC_CANONICAL_SYSTEM
 
diff --git a/console/yap.c b/console/yap.c
index 333602cc1..7d318e4e2 100644
--- a/console/yap.c
+++ b/console/yap.c
@@ -226,9 +226,9 @@ parse_yap_arguments(int argc, char *argv[], yap_init_args *init_args)
             fprintf(stderr,"  -?   Shows this screen\n");
             fprintf(stderr,"  -b   Boot file (%s)\n", StartUpFile);
             fprintf(stderr,"  -l   Prolog file\n");
-            fprintf(stderr,"  -h   Heap area in Kbytes (default: %d)\n", DefHeapSpace);
-	    fprintf(stderr,"  -s   Stack area in Kbytes (default: %d)\n", DefStackSpace);
-	    fprintf(stderr,"  -t   Trail area in Kbytes (default: %d)\n", DefTrailSpace);
+            fprintf(stderr,"  -h   Heap area in Kbytes (default: %d, minimum: %d)\n", DefHeapSpace, MinHeapSpace);
+	    fprintf(stderr,"  -s   Stack area in Kbytes (default: %d, minimum: %d)\n", DefStackSpace, MinStackSpace);
+	    fprintf(stderr,"  -t   Trail area in Kbytes (default: %d, minimum: %d)\n", DefTrailSpace, MinTrailSpace);
             fprintf(stderr,"  -w   YapOr option: Number of workers (default: %d)\n", init_args->NumberWorkers);
             fprintf(stderr,"  -sl  YapOr option: Loop scheduler executions before look for hiden shared work (default: %d)\n", init_args->SchedulerLoop);
             fprintf(stderr,"  -d   YapOr option: Value of delayed release of load (default: %d)\n", init_args->DelayedReleaseLoad);