diff --git a/tests/suites/target_test.function b/tests/suites/target_test.function
index 4d03c3be56..89835d2bff 100644
--- a/tests/suites/target_test.function
+++ b/tests/suites/target_test.function
@@ -90,15 +90,15 @@ uint8_t receive_byte()
 uint32_t receive_uint32()
 {
     uint32_t value;
-    uint8_t c_be[8] = { greentea_getc(),
-                        greentea_getc(),
-                        greentea_getc(),
-                        greentea_getc(),
-                        greentea_getc(),
-                        greentea_getc(),
-                        greentea_getc(),
-                        greentea_getc()
-                      };
+    const uint8_t c_be[8] = { greentea_getc(),
+                              greentea_getc(),
+                              greentea_getc(),
+                              greentea_getc(),
+                              greentea_getc(),
+                              greentea_getc(),
+                              greentea_getc(),
+                              greentea_getc()
+                             };
     const uint8_t c[9] = { c_be[6], c_be[7], c_be[4], c_be[5], c_be[2],
                            c_be[3], c_be[0], c_be[1], '\0' };
     TEST_HELPER_ASSERT( unhexify( (uint8_t*)&value, c ) != 8 );