diff --git a/dlib/test/matrix2.cpp b/dlib/test/matrix2.cpp
index bbe605ee1..58db5bfc7 100644
--- a/dlib/test/matrix2.cpp
+++ b/dlib/test/matrix2.cpp
@@ -409,7 +409,7 @@ namespace
         DLIB_TEST(abs(det(dm7) - det(m7)) < 1e-14);
         DLIB_TEST(abs(min(dm7) - min(m7)) < 1e-14);
         DLIB_TEST(abs(max(dm7) - max(m7)) < 1e-14);
-        DLIB_TEST_MSG(abs(sum(dm7) - sum(m7)) < 1e-14,sum(dm7) - sum(m7));
+        DLIB_TEST_MSG(abs(sum(dm7) - sum(m7)) < 1e-13,sum(dm7) - sum(m7));
         DLIB_TEST(abs(prod(dm7) -prod(m7)) < 1e-14);
         DLIB_TEST(equal(diag(dm7) , diag(m7)));
         DLIB_TEST(equal(trans(dm7) , trans(m7)));