diff --git a/build-common.sh b/build-common.sh
index e25cfec..0dfc202 100644
--- a/build-common.sh
+++ b/build-common.sh
@@ -110,8 +110,12 @@ cleanup_site_packages() {
     fi
 
     # ── NumPy ────────────────────────────────────────────────
-    # Remove unused submodules (only core, fft, random are used)
-    for mod in polynomial linalg ma lib distutils f2py typing _pyinstaller; do
+    # Only strip modules that are safely unused by numpy's own import chain.
+    # DO NOT strip: lib, linalg, ma, matrixlib — numpy.__init__ imports them
+    # transitively (e.g. matrixlib → defmatrix → linalg), so removing any of
+    # these breaks `import numpy` itself, cascading into every downstream
+    # module. Learned the hard way in the v0.0.0.dev0 Windows build.
+    for mod in polynomial distutils f2py typing _pyinstaller; do
         rm -rf "$sp_dir/numpy/$mod" 2>/dev/null || true
     done
     rm -rf "$sp_dir/numpy/tests" "$sp_dir/numpy/*/tests" 2>/dev/null || true