diff --git a/usr/klibc/malloc.c b/usr/klibc/malloc.c
index abda84c..09a596f 100644
--- a/usr/klibc/malloc.c
+++ b/usr/klibc/malloc.c
@@ -171,6 +171,10 @@
 	fsize = (size + MALLOC_CHUNK_MASK) & ~MALLOC_CHUNK_MASK;
 
 #if _KLIBC_MALLOC_USES_SBRK
+	if (fsize > INTPTR_MAX) {
+		errno = ENOMEM;
+		return NULL;
+	}
 	fp = (struct free_arena_header *)sbrk(fsize);
 #else
 	fp = (struct free_arena_header *)