diff --git a/modules/src/malloc/check.c b/modules/src/malloc/check.c
index 4a5225c2c..1611b0872 100644
--- a/modules/src/malloc/check.c
+++ b/modules/src/malloc/check.c
@@ -65,7 +65,7 @@ acquire_malout()	{
 	static char buf[BUFSIZ];
 	
 	if (!malout)	{
-		malout = fopen("mal.out", "w");	
+		malout = freopen("mal.out", "w", stderr);	
 		setbuf(malout, buf);
 	}
 }
@@ -156,7 +156,7 @@ check_mallinks(s) char *s;	{
 	stat = BEZET;
 	for_all_mallinks(ml)	{
 		if (checksum_of(ml) != checksum(ml))
-			Error("mallink info at %ld corrupted", s, ml);
+			Error("mallink info at %lx corrupted", s, (long)ml);
 		if (working_on(ml))	{
 			stat = BEZET;
 			continue;
@@ -164,15 +164,15 @@ check_mallinks(s) char *s;	{
 		if (	!last_mallink(ml) &&
 			phys_prev_of(phys_next_of(ml)) != ml
 		)
-			Error("upward chain bad at %ld", s, ml);
+			Error("upward chain bad at %lx", s, (long)ml);
 		if (	!first_mallink(ml) &&
 			phys_next_of(phys_prev_of(ml)) != ml
 		)
-			Error("downward chain bad at %ld", s, ml);
+			Error("downward chain bad at %lx", s, (long)ml);
 		if (free_of(ml))	{
 			if (stat == VRIJ)
-				Error("free mallink at %ld follows free mallink",
-								s, ml);
+				Error("free mallink at %lx follows free mallink",
+								s, (long)ml);
 			stat = VRIJ;
 		}
 		else
@@ -185,29 +185,29 @@ check_mallinks(s) char *s;	{
 			if (working_on(ml))
 				continue;
 			if (!free_of(ml))
-				Error("occupied mallink %ld occurs in free_list", s, ml);
+				Error("occupied mallink %lx occurs in free_list", s, (long)ml);
 			switch (mark_of(ml))	{
 			case IN_ML_LAST:
 				set_mark(ml, IN_FREE_LIST);
 				break;
 			case IN_FREE_LIST:
-				Error("mallink %ld occurs in 2 free_lists",
-								s, ml);
+				Error("mallink %lx occurs in 2 free_lists",
+								s, (long)ml);
 			default:
-				Error("unknown mallink %ld in free_list",
-								s, ml);
+				Error("unknown mallink %lx in free_list",
+								s, (long)ml);
 			}
 			if (size_of(ml) < size)
-				Error("size of mallink %ld too small", s, ml);
+				Error("size of mallink %lx too small", s, (long)ml);
 			if (size_of(ml) >= 2*size)
-				Error("size of mallink %ld too large", s, ml);
+				Error("size of mallink %lx too large", s, (long)ml);
 		}
 	}
 	for_all_mallinks (ml)	{
 		if (working_on(ml))
 			continue;
 		if (free_of(ml) && mark_of(ml) != IN_FREE_LIST)
-			Error("free mallink %ld is in no free_list", s, ml);
+			Error("free mallink %lx is in no free_list", s, (long)ml);
 		set_mark(ml, CLEAR);
 	}
 }
diff --git a/modules/src/malloc/mal.c b/modules/src/malloc/mal.c
index c1c51e63a..dd8d221f6 100644
--- a/modules/src/malloc/mal.c
+++ b/modules/src/malloc/mal.c
@@ -172,6 +172,7 @@ free(addr)
 		set_log_next(ml, *stp);
 		*stp = ml;
 		set_store(ml, 1);
+		calc_checksum(ml);
 		check_mallinks("free fast exit");
 	}
 	else	{
@@ -262,6 +263,7 @@ realloc(addr, n)
 		if (! stp1) store[(size_of(ml) >> LOG_MIN_SIZE) - 1] = stp;
 		else set_log_next(stp1, stp);
 		set_store(ml, 0);
+		calc_checksum(ml);
 	}
 #endif
 	if (free_of(ml)) {
diff --git a/modules/src/malloc/phys.h b/modules/src/malloc/phys.h
index aa05c975e..e5dc277bd 100644
--- a/modules/src/malloc/phys.h
+++ b/modules/src/malloc/phys.h
@@ -18,19 +18,19 @@ publicdata mallink *ml_last;
 
 #define __bits(ml)		((size_type)_phys_prev_of(ml) & BITS)
 #define	__free_of(ml)		((size_type)_phys_prev_of(ml) & FREE_BIT)
-#define __phys_prev_of(ml)	(mallink *)((size_type)_phys_prev_of(ml) & ~FREE_BIT)
+#define __phys_prev_of(ml)	(mallink *)((size_type)_phys_prev_of(ml) & ~BITS)
 #define prev_size_of(ml)	((char *)(ml) - \
 				 (char *)__phys_prev_of(ml) - \
 				 mallink_size() \
 				)
 #define	set_phys_prev(ml,e) \
-	(_phys_prev_of(ml) = (mallink *) ((char *)e + __free_of(ml)))
+	(_phys_prev_of(ml) = (mallink *) ((char *)e + __bits(ml)))
 
 #ifdef	CHECK
 public Error();
 #define	phys_prev_of(ml)	(mallink *) \
 	(first_mallink(ml) ? \
-		(char *)Error("phys_prev_of first_mallink %ld", "somewhere", ml) : \
+		(char *)Error("phys_prev_of first_mallink %lx", "somewhere", (long)ml) : \
 		(char *)__phys_prev_of(ml) \
 	)
 #else	ndef	CHECK