diff --git a/tools/profiling/microbenchmarks/bm_diff.py b/tools/profiling/microbenchmarks/bm_diff.py
index 93999af520a..9f85d47ab42 100755
--- a/tools/profiling/microbenchmarks/bm_diff.py
+++ b/tools/profiling/microbenchmarks/bm_diff.py
@@ -35,6 +35,7 @@ import tabulate
 import argparse
 import scipy
 import subprocess
+import multiprocessing
 
 def changed_ratio(n, o):
   if float(o) <= .0001: o = 0