diff --git a/bin/build b/bin/build
index b7bb7d9..c19cbba 100755
--- a/bin/build
+++ b/bin/build
@@ -133,9 +133,23 @@ if 1: # has MPW
 
 # Tell MPW what to do when it starts (can use {Src} in their -c command)
 if config.passthru:
-    bootscript = 'Set Src Disk:Src:; Export Src; Directory {Src}\r'
-    bootscript += 'Set Exit 0; %s; Quit\r' % config.passthru
-    vol['MPW']['UserStartup'].data = bootscript.encode('mac_roman')
+    bootscript = '''
+        Set Src Disk:Src:
+        Export Src
+        Directory {{Src}}
+        Set Exit 0
+
+        ''' + {config.passthru} + '''
+
+        # DumpObj SeriousFile.c.o to SeriousFile.c.d
+        Files -r -o -f -t 'OBJ ' -c 'MPS ' Disk:Src:BuildResults | StreamEdit ∂
+            -e "1,$ change 'If ∂`Newer ' . ' ' . '.dump∂`; DumpObj ' . '>' . '.dump; End'; replace -c 2 /[a-z]+.dump/ 'd'" ∂
+            >Disk:DumpObjScript
+        Disk:DumpObjScript
+
+        Quit
+    '''
+    vol['MPW']['UserStartup'].data = bootscript.replace('\n', '\r').encode('mac_roman')
 
 # Evil tuning: more RAM for MPW because some tools do not use temp mem
 mpw = list(macresources.parse_file(vol['MPW']['MPW Shell'].rsrc))