diff --git a/benchmark/gemm3m.c b/benchmark/gemm3m.c
index d39543585..f4048c436 100644
--- a/benchmark/gemm3m.c
+++ b/benchmark/gemm3m.c
@@ -181,9 +181,9 @@ 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;
-			b[i + j * m * COMPSIZE] = ((FLOAT) rand() / (FLOAT) RAND_MAX) - 0.5;
-			c[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;
+			b[(long)i + (long)j * (long)m * COMPSIZE] = ((FLOAT) rand() / (FLOAT) RAND_MAX) - 0.5;
+			c[(long)i + (long)j * (long)m * COMPSIZE] = ((FLOAT) rand() / (FLOAT) RAND_MAX) - 0.5;
       		}
     	}