diff --git a/src/linux/brk.c b/src/linux/brk.c
index 9f63c5a..c261518 100644
--- a/src/linux/brk.c
+++ b/src/linux/brk.c
@@ -2,5 +2,5 @@
 
 int brk(void *end)
 {
-	return -(syscall(SYS_brk, end) == -1);
+	return -((void *)syscall(SYS_brk, end) != end);
 }
diff --git a/src/linux/sbrk.c b/src/linux/sbrk.c
index b2943a9..478a35e 100644
--- a/src/linux/sbrk.c
+++ b/src/linux/sbrk.c
@@ -3,5 +3,11 @@
 
 void *sbrk(ptrdiff_t inc)
 {
-	return (void *)syscall(SYS_brk, syscall(SYS_brk, 0)+inc);
+	void *p = (void *)syscall(SYS_brk, 0);
+
+	if (inc == 0)
+		return p;
+	if ((void *)syscall(SYS_brk, p+inc) == p+inc)
+		return p;
+	return (void *)-1;
 }