diff --git a/benchmark/n_body_creation.cpp b/benchmark/n_body_creation.cpp
index 1c2de46ae..b2d55192d 100644
--- a/benchmark/n_body_creation.cpp
+++ b/benchmark/n_body_creation.cpp
@@ -66,7 +66,7 @@ int main(int argc, char *argv[])
 
     auto counter = 0u;
     for (const auto &ex : ta.get_decomposition()) {
-        std::cout << "u_" << counter++ << " = " << ex << '\n';
+        std::cout << "u_" << counter++ << " = " << ex.first << '\n';
     }
 
     std::cout << "Construction time: " << elapsed << "ms\n";
diff --git a/src/expression.cpp b/src/expression.cpp
index 3d769ad36..deb30acce 100644
--- a/src/expression.cpp
+++ b/src/expression.cpp
@@ -224,6 +224,10 @@ expression operator+(expression e1, expression e2)
                 // e1 + 0 = e1.
                 return expression{std::forward<decltype(v1)>(v1)};
             }
+            if (std::visit([](const auto &x) { return x < 0; }, v2.value())) {
+                // e1 + -x = e1 - x.
+                return expression{std::forward<decltype(v1)>(v1)} - expression{-std::forward<decltype(v2)>(v2)};
+            }
             // NOTE: fall through the standard case if e2 is not zero.
         }
 
@@ -257,6 +261,10 @@ expression operator-(expression e1, expression e2)
                 // e1 - 0 = e1.
                 return expression{std::forward<decltype(v1)>(v1)};
             }
+            if (std::visit([](const auto &x) { return x < 0; }, v2.value())) {
+                // e1 - -x = e1 + x.
+                return expression{std::forward<decltype(v1)>(v1)} + expression{-std::forward<decltype(v2)>(v2)};
+            }
             // NOTE: fall through the standard case if e2 is not zero.
         }
 
diff --git a/test/expression.cpp b/test/expression.cpp
index 1b8afc8b2..639bdc51c 100644
--- a/test/expression.cpp
+++ b/test/expression.cpp
@@ -396,3 +396,11 @@ TEST_CASE("get_param_size")
     REQUIRE(get_param_size(par[122] + par[123]) == 124u);
     REQUIRE(get_param_size(par[500] - sin(cos(par[1] + "y"_var) + par[4])) == 501u);
 }
+
+TEST_CASE("binary simpls")
+{
+    auto [x, y] = make_vars("x", "y");
+
+    REQUIRE(x + -1. == x - 1.);
+    REQUIRE(y - -1. == y + 1.);
+}