diff --git a/rtengine/labimage.cc b/rtengine/labimage.cc
index 29585ca0c..c33961bff 100644
--- a/rtengine/labimage.cc
+++ b/rtengine/labimage.cc
@@ -43,14 +43,14 @@ void LabImage::CopyFrom(LabImage *Img)
     #pragma omp parallel sections
     {
         #pragma omp section
-        memcpy(L[0], Img->L[0], W * H * 1 * sizeof(float));
+        memcpy(L[0], Img->L[0], static_cast<std::size_t>(W) * H * sizeof(float));
         #pragma omp section
-        memcpy(a[0], Img->a[0], W * H * 1 * sizeof(float));
+        memcpy(a[0], Img->a[0], static_cast<std::size_t>(W) * H * sizeof(float));
         #pragma omp section
-        memcpy(b[0], Img->b[0], W * H * 1 * sizeof(float));
+        memcpy(b[0], Img->b[0], static_cast<std::size_t>(W) * H * sizeof(float));
     }
 #else
-    memcpy(data, Img->data, W * H * 3 * sizeof(float));
+    memcpy(data, Img->data, static_cast<std::size_t>(W) * H * 3 * sizeof(float));
 #endif
 }