diff --git a/build/meta-usr/recipes-usr/so3/usr-so3_1.0.bb b/build/meta-usr/recipes-usr/so3/usr-so3_1.0.bb
index c2ac3e933f..9738ccadee 100644
--- a/build/meta-usr/recipes-usr/so3/usr-so3_1.0.bb
+++ b/build/meta-usr/recipes-usr/so3/usr-so3_1.0.bb
@@ -76,11 +76,18 @@ python do_deploy() {
     d.setVar('ROOTFS_FILENAME', '')
 
     if os.path.isdir(d.getVar('IB_ROOTFS_PATH')):
-        __do_rootfs_mount(d)
-        
         src_dir = os.path.join(d.getVar('IB_TARGET'), 'build', 'deploy')
         dst_dir = os.path.join(d.getVar('IB_ROOTFS_PATH'), 'fs')
 
+        # The user space must be built before it can be deployed. Bail out
+        # early — before mounting the rootfs, so a missing build does not
+        # leave a dangling loop mount — with an actionable message.
+        if not os.path.isdir(src_dir):
+            bb.fatal("SO3 user space not built: '%s' is missing. "
+                     "Build it first with 'build.sh -x usr-so3' (or 'build.sh bsp-so3')." % src_dir)
+
+        __do_rootfs_mount(d)
+
         # The SO3 rootfs.fat is loop-mounted at rootfs/fs as root
         # (rootfs/mount.sh), so the copy must be privileged. The split
         # debug-info files (*.debug) are host-side gdb symbols, not