diff --git a/core/cfs/cfs-coffee.c b/core/cfs/cfs-coffee.c
index 79eb18d94..37b1a707e 100644
--- a/core/cfs/cfs-coffee.c
+++ b/core/cfs/cfs-coffee.c
@@ -1055,7 +1055,12 @@ cfs_seek(int fd, cfs_offset_t offset, int whence)
   }
 
   if(fdp->file->end < new_offset) {
-    fdp->file->end = new_offset;
+    if(FD_WRITABLE(fd)) {
+      fdp->file->end = new_offset;
+    } else {
+      /* Disallow seeking past the end of the file for read only FDs */
+      return (cfs_offset_t)-1;
+    }
   }
 
   return fdp->offset = new_offset;