diff --git a/manticore/platforms/linux.py b/manticore/platforms/linux.py
index 49a1f59..18161c8 100644
--- a/manticore/platforms/linux.py
+++ b/manticore/platforms/linux.py
@@ -1312,8 +1312,8 @@ class Linux(Platform):
         if brk != 0 and brk != self.elf_brk:
             mem = self.current.memory
             size = brk - self.elf_brk
-            perms = mem.perms(self.elf_brk - 1)
             if brk > mem._ceil(self.elf_brk):
+                perms = mem.perms(self.elf_brk - 1)
                 addr = mem.mmap(mem._ceil(self.elf_brk), size, perms)
                 assert mem._ceil(self.elf_brk) == addr, "Error in brk!"
             self.elf_brk += size