diff --git a/spike/x86/survey.sh b/spike/x86/survey.sh
index 7fe1aa2..1eb0fdd 100755
--- a/spike/x86/survey.sh
+++ b/spike/x86/survey.sh
@@ -82,6 +82,9 @@ declare -a match=() differ=() refused=() nox86=() skip=()
 
 for src in "$corpus"/test/programs/*.flan "$corpus"/spike/x86/*.flan \
          "$corpus"/spike/js/*.flan; do
+  # An unmatched glob comes through as its own pattern; a corpus that is
+  # missing one of these directories is a smaller sweep, not an error.
+  [ -e "$src" ] || continue
   name=$(basename "$src" .flan)
   if [ $# -gt 0 ]; then
     want=0
diff --git a/test/dune b/test/dune
index 6ee3325..1f2004e 100644
--- a/test/dune
+++ b/test/dune
@@ -196,6 +196,11 @@
  (deps
   (file %{workspace_root}/spike/x86/survey.sh)
   (glob_files %{workspace_root}/spike/x86/*.flan)
+  ; The js spike's programs are plain flan programs and the sweep reads them
+  ; now, so they have to be in the build tree the sweep runs from -- otherwise
+  ; the glob matches nothing, and nothing is exactly what it was reporting
+  ; while p1-int-semantics.flan sat there with a wrong shift in it.
+  (glob_files %{workspace_root}/spike/js/*.flan)
   (file %{workspace_root}/bin/main.exe)
   (file %{workspace_root}/calc-me.flan)
   (file %{workspace_root}/sand.flan)