diff --git a/src/main/c/densitystep.c b/src/main/c/densitystep.c
index 385dc4e..7951f27 100644
--- a/src/main/c/densitystep.c
+++ b/src/main/c/densitystep.c
@@ -120,6 +120,7 @@ void advectDensity(JNIEnv * env, uint32_t chunk_mask, int N, int b, jobjectArray
     for(k=1; k<N-1; k++){
         for(j=1; j<N-1; j++){
             for(i=1; i<N-1; i++){
+                sampleArr = d0;
                 //calculate location to pull from
                 x = i-dtx*u[IX(i,j,k)];
                 y = j-dty*v[IX(i,j,k)];