diff --git a/exercises/20_class_template/main.cpp b/exercises/20_class_template/main.cpp
index fafc1b19..d1dc449d 100644
--- a/exercises/20_class_template/main.cpp
+++ b/exercises/20_class_template/main.cpp
@@ -49,7 +49,7 @@ int main(int argc, char **argv) {
         auto t0 = Tensor4D(shape, data);
         auto t1 = Tensor4D(shape, data);
         t0 += t1;
-        for (unsigned int i = 0; i < sizeof(data) / sizeof(int); i++) {
+        for (auto i = 0u; i < sizeof(data) / sizeof(int); ++i) {
             ASSERT(t0.data[i] == data[i] * 2, "Tensor doubled by plus its self.");
         }
     }
@@ -80,7 +80,7 @@ int main(int argc, char **argv) {
         auto t0 = Tensor4D(s0, d0);
         auto t1 = Tensor4D(s1, d1);
         t0 += t1;
-        for (unsigned int i = 0; i < sizeof(d0) / sizeof(int); i++) {
+        for (auto i = 0u; i < sizeof(d0) / sizeof(int); ++i) {
             ASSERT(t0.data[i] == 7.f, "Every element of t0 should be 7 after adding t1 to it.");
         }
     }
@@ -102,8 +102,8 @@ int main(int argc, char **argv) {
         auto t0 = Tensor4D(s0, d0);
         auto t1 = Tensor4D(s1, d1);
         t0 += t1;
-        for (unsigned int i = 0; i < sizeof(d0) / sizeof(int); i++) {
-            ASSERT(t0.data[i] == t0.data[i] + 1, "Every element of t0 should be incremented by 1 after adding t1 to it.");
+        for (auto i = 0u; i < sizeof(d0) / sizeof(int); ++i) {
+            ASSERT(t0.data[i] == d0[i] + 1, "Every element of t0 should be incremented by 1 after adding t1 to it.");
         }
     }
 }