diff --git a/rtengine/iplab2rgb.cc b/rtengine/iplab2rgb.cc
index 2de95523c..981290279 100644
--- a/rtengine/iplab2rgb.cc
+++ b/rtengine/iplab2rgb.cc
@@ -124,9 +124,12 @@ void ImProcFunctions::lab2rgb (LabImage* lab, Image8* image) {
 				xyz2srgb(x_,y_,z_,R,G,B);
 
 				/* copy RGB */
+				 #pragma omp critical 
+				 {
 				image->data[ix++] = (int)gamma2curve[(R)] >> 8;
 				image->data[ix++] = (int)gamma2curve[(G)] >> 8;
 				image->data[ix++] = (int)gamma2curve[(B)] >> 8;
+				}
 			}
 		}
 	}