diff --git a/simgear/math/simd.hxx b/simgear/math/simd.hxx
index e0a20120..690ba48f 100644
--- a/simgear/math/simd.hxx
+++ b/simgear/math/simd.hxx
@@ -94,8 +94,8 @@ public:
     }
     template<int M>
     simd4_t(const simd4_t<T,M>& v) {
-        if (M<4) std::memset(_v4+M, 0, sizeof(T[4-M]));
         std::memcpy(vec, v.ptr(), sizeof(T[M]));
+        for (int i=N; i<4; i++) _v4[i] = 0;
     }
     ~simd4_t(void) {}