diff --git a/sys/src/libsat/misc.c b/sys/src/libsat/misc.c
index e7e843529..f62aed431 100644
--- a/sys/src/libsat/misc.c
+++ b/sys/src/libsat/misc.c
@@ -106,6 +106,7 @@ satrealloc(SATSolve *s, void *v, ulong n)
 	v = realloc(v, n);
 	if(v == nil)
 		saterror(s, "realloc: %r");
+	setmalloctag(v, getcallerpc(&s));
 	return v;
 }
 
diff --git a/sys/src/libsat/satsolve.c b/sys/src/libsat/satsolve.c
index 94dec8598..78728fc8c 100644
--- a/sys/src/libsat/satsolve.c
+++ b/sys/src/libsat/satsolve.c
@@ -82,7 +82,7 @@ solvinit(SATSolve *s)
 {
 	satdebuginit(s);
 	satheapreset(s);
-	s->decbd = satrealloc(s, s->decbd, s->nvar * sizeof(int));
+	s->decbd = satrealloc(s, s->decbd, (s->nvar + 1) * sizeof(int));
 	s->decbd[0] = 0;
 	s->trail = satrealloc(s, s->trail, sizeof(int) * s->nvar);
 	s->fullrlits = satrealloc(s, s->fullrlits, sizeof(int) * s->nvar);