diff --git a/test/syscalls/linux/mmap.cc b/test/syscalls/linux/mmap.cc
index e9892e5dc..b07c3e4a3 100644
--- a/test/syscalls/linux/mmap.cc
+++ b/test/syscalls/linux/mmap.cc
@@ -1211,16 +1211,14 @@ TEST_F(MMapFileTest, WriteSharedTruncateUp) {
   std::string first(kPageSize / 2, 'A');
   memcpy(reinterpret_cast<void*>(addr), first.c_str(), first.size());
 
-  // Second half; this is not reflected in the file now (see
-  // WriteSharedBeyondEnd), but will be after the truncate.
+  // Extend the file to a full page.
+  EXPECT_THAT(ftruncate(fd_.get(), kPageSize), SyscallSucceeds());
+
+  // Second half; this will be reflected in the file now.
   std::string second(kPageSize / 2, 'B');
   memcpy(reinterpret_cast<void*>(addr + kPageSize / 2), second.c_str(),
          second.size());
 
-  // Extend the file to a full page. The second half of the page will be
-  // reflected in the file.
-  EXPECT_THAT(ftruncate(fd_.get(), kPageSize), SyscallSucceeds());
-
   // The file may not actually be updated until munmap is called.
   ASSERT_THAT(Unmap(), SyscallSucceeds());