diff --git a/src/libcoreint/opcodes-ecma-arithmetics.c b/src/libcoreint/opcodes-ecma-arithmetics.c
index c086514ea..24850195c 100644
--- a/src/libcoreint/opcodes-ecma-arithmetics.c
+++ b/src/libcoreint/opcodes-ecma-arithmetics.c
@@ -322,16 +322,10 @@ opfunc_unary_plus (opcode_t opdata, /**< operation data */
   ECMA_TRY_CATCH (var_value, get_variable_value (int_data, var_idx, false), ret_value);
   ECMA_TRY_CATCH (num_value, ecma_op_to_number (var_value.u.value), ret_value);
 
-  ecma_number_t *var_p, *res_p;
-  var_p = (ecma_number_t*) ECMA_GET_POINTER (num_value.u.value.value);
-
-  res_p = ecma_alloc_number ();
-  *res_p = *var_p;
+  ecma_number_t *var_p = (ecma_number_t*) ECMA_GET_POINTER (num_value.u.value.value);
   ret_value = set_variable_value (int_data,
                                   dst_var_idx,
-                                  ecma_make_number_value (res_p));
-
-  ecma_dealloc_number (res_p);
+                                  ecma_make_number_value (var_p));
 
   ECMA_FINALIZE (num_value);
   ECMA_FINALIZE (var_value);
@@ -365,7 +359,14 @@ opfunc_unary_minus (opcode_t opdata, /**< operation data */
   var_p = (ecma_number_t*) ECMA_GET_POINTER (num_value.u.value.value);
 
   res_p = ecma_alloc_number ();
-  *res_p = ecma_number_negate (*var_p);
+  if (ecma_number_is_nan (*var_p))
+  {
+    *res_p = *var_p;
+  }
+  else
+  {
+    *res_p = ecma_number_negate (*var_p);
+  }
   ret_value = set_variable_value (int_data,
                                   dst_var_idx,
                                   ecma_make_number_value (res_p));
diff --git a/tests/jerry/unary_plus_minus.js b/tests/jerry/unary_plus_minus.js
index 874e582d0..433185997 100644
--- a/tests/jerry/unary_plus_minus.js
+++ b/tests/jerry/unary_plus_minus.js
@@ -16,3 +16,4 @@ assert (+0 === -0);
 assert (1/-0 === -Infinity);
 assert (1/+0 === Infinity);
 assert ("3" -+-+-+ "1" + "1" / "3" * "6" + "2" === "42");
+assert (isNaN (-NaN));
\ No newline at end of file