diff --git a/benchmark/spmv.c b/benchmark/spmv.c
index 12a33e298..2a26c9416 100644
--- a/benchmark/spmv.c
+++ b/benchmark/spmv.c
@@ -178,7 +178,7 @@ int main(int argc, char *argv[]){
 
    for(j = 0; j < m; j++){
       		for(i = 0; i < m * COMPSIZE; i++){
-			a[i + j * m * COMPSIZE] = ((FLOAT) rand() / (FLOAT) RAND_MAX) - 0.5;
+			a[(long)i + (long)j * (long)m * COMPSIZE] = ((FLOAT) rand() / (FLOAT) RAND_MAX) - 0.5;
       		}
    }