diff --git a/modules/imgproc/perf/perf_contours.cpp b/modules/imgproc/perf/perf_contours.cpp
index 7606605cce..d3a70cfdd7 100644
--- a/modules/imgproc/perf/perf_contours.cpp
+++ b/modules/imgproc/perf/perf_contours.cpp
@@ -3,7 +3,7 @@
 // of this distribution and at http://opencv.org/license.html.
 #include "perf_precomp.hpp"
 
-namespace opencv_test {
+namespace opencv_test { namespace {
 
 CV_ENUM(RetrMode, RETR_EXTERNAL, RETR_LIST, RETR_CCOMP, RETR_TREE)
 CV_ENUM(ApproxMode, CHAIN_APPROX_NONE, CHAIN_APPROX_SIMPLE, CHAIN_APPROX_TC89_L1, CHAIN_APPROX_TC89_KCOS)
@@ -84,4 +84,4 @@ PERF_TEST_P(TestFindContoursFF, findContours,
     SANITY_CHECK_NOTHING();
 }
 
-} // namespace
+} } // namespace