diff --git a/src/os_unix.h b/src/os_unix.h
index 99184ab..fac2c0f 100644
--- a/src/os_unix.h
+++ b/src/os_unix.h
@@ -488,3 +488,9 @@
 
 // We have three kinds of ACL support.
 #define HAVE_ACL (HAVE_POSIX_ACL || HAVE_SOLARIS_ACL || HAVE_AIX_ACL)
+
+struct cellsize {
+    unsigned int cs_xpixel;
+    unsigned int cs_ypixel;
+};
+