diff --git a/include/crucible/fd.h b/include/crucible/fd.h
index 685babd..8492846 100644
--- a/include/crucible/fd.h
+++ b/include/crucible/fd.h
@@ -70,10 +70,11 @@ namespace crucible {
 	string mmap_flags_ntoa(int flags);
 
 	// Unlink, rename
-	void unlink_or_die(const string &file);
 	void rename_or_die(const string &from, const string &to);
 	void renameat_or_die(int fromfd, const string &frompath, int tofd, const string &topath);
 
+	void ftruncate_or_die(int fd, off_t size);
+
 	// Read or write structs:
 	// There is a template specialization to read or write strings
 	// Three-arg version of read_or_die/write_or_die throws an error on incomplete read/writes
diff --git a/lib/fd.cc b/lib/fd.cc
index 881f98a..e0735a9 100644
--- a/lib/fd.cc
+++ b/lib/fd.cc
@@ -230,6 +230,14 @@ namespace crucible {
 		}
 	}
 
+	void
+	ftruncate_or_die(int fd, off_t size)
+	{
+		if (::ftruncate(fd, size)) {
+			THROW_ERRNO("ftruncate: " << name_fd(fd) << " size " << size);
+		}
+	}
+
 	string
 	socket_domain_ntoa(int domain)
 	{