diff --git a/scripts/build.sh b/scripts/build.sh
index de29a14..4d351f3 100644
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -171,6 +171,12 @@ for f in $(grep -l "unique_ptr" src/*.h 2>/dev/null || true); do
   grep -q "<memory>" "$f" || sed -i '1i #include <memory>' "$f"
 done
 
+# 4c. Fix Vec3.cpp: in the #else (glm) branch, toOf() incorrectly returns
+#     ofVec3f instead of glm::vec3 — a bug in ofxPiMapper upstream.
+sed -i '/^#else/,/^#endif/{
+  s/return ofVec3f(x, y, z);/return glm::vec3(x, y, z);/
+}' src/Types/Vec3.cpp
+
 # ── 5. Cross-compile ofxPiMapper for aarch64 ────────────────────────────────
 # OF's Makefile supports PLATFORM_ARCH and CROSS_COMPILING as make variables —
 # no need to fake uname. Passing them directly bypasses the uname -m check.