diff --git a/build b/build
index ac1b5828..deee6e64 100755
--- a/build
+++ b/build
@@ -106,7 +106,10 @@ older_than subx_bin subx.cc *_list && {
   $CXX $CFLAGS subx.cc -o subx_bin
 }
 
-if [ $# -eq 0 ]
+# We ought to always rebuild all apps if any .subx layers are updated.
+# But during development it's too slow to update _all_ apps when we're
+# repeatedly running a single one.
+if [ $ALL ]
 then
 
   # Assumption: SubX programs don't need to be retranslated every time we
diff --git a/ntranslate b/ntranslate
index 24d87056..104d2001 100755
--- a/ntranslate
+++ b/ntranslate
@@ -14,7 +14,7 @@
 set -e
 set -v
 
-./build
+ALL=1 ./build
 
 echo `cat $* |grep -v '^\s*#\|^\s*$' |wc -l` lines
 
diff --git a/translate b/translate
index 7acf92c4..4838f1d2 100755
--- a/translate
+++ b/translate
@@ -14,7 +14,7 @@
 set -e
 set -v
 
-./build
+ALL=1 ./build
 
 echo `cat $* |grep -v '^\s*#\|^\s*$' |wc -l` lines