diff --git a/Changes.md b/Changes.md
index 86e7c79b5..5be996cc0 100644
--- a/Changes.md
+++ b/Changes.md
@@ -5,6 +5,9 @@ MAD-X release 5.09.02 (2024.??.??)
     * Fixed an issue where the IBS table would only be created if the `FILE="STRING"` part of the command was provided, instead of always as documented.
     * Added an export of the `ibs.coulog` and `ibs.const` variables after calling the IBS command (see user guide).
     * Documented the IBS code.
+* Add2expr
+  * [PR1 1211] (https://github.com/MethodicalAcceleratorDesign/MAD-X/pull/1211) Evaluates the expression when defined.
+    * Previously it was possible to add as syntax error in the expression and this was only detected when the expression was evaluated. This PR fixes that. 
 
 
 MAD-X release 5.09.01 (2023.12.04)
diff --git a/src/mad_cmd.c b/src/mad_cmd.c
index 7b2677707..35d94342e 100644
--- a/src/mad_cmd.c
+++ b/src/mad_cmd.c
@@ -763,57 +763,45 @@ add_to_command_list_list(char* label, struct command_list* cl, struct command_li
 void exec_add_expression(struct in_cmd* cmd){
   char* varname = command_par_string_user("var", cmd->clone);
   char* expchar = command_par_string_user("expr", cmd->clone);
-  if(expchar==NULL){
+  //const char whitespace[] = " \f\n\r\t\v";
+  struct variable* var;
+  char in_string_tmp[100];
+  char tmp_var_expr[50
+    ];
+
+  if (expchar==NULL){
     warning("Need to add an expression for: ", varname);
     return;
-  }
-  struct variable* var;
-  struct expression* expr1, *expr2; 
-  struct expression* exprcomb;
+  } 
+  //create an input string starting with the varname
+  strcpy(in_string_tmp, varname);
+  strcat(in_string_tmp, ":= ");
+  
+  //Adds the varialbe expression or valube in case it is not an expression
   if ((var = find_variable(varname, variable_list)) == NULL) {
-      var = new_variable(varname, 0, 1, 2, NULL, NULL);
-      add_to_var_list(var, variable_list, 1);
+    strcpy(tmp_var_expr, " ");
   }
-
-  if ((var = find_variable(varname, variable_list)) != NULL){
-      
-    if(var->type==2){
-      if(var->expr==NULL){
-
-        char *result = malloc(100 * sizeof(char));
-        sprintf(result, "%.16f", var->value);
-        expr1 = new_expression(result,NULL);
-        free(result);
-        var->expr = mymalloc("add expression", sizeof *var->expr);
-      }
-      else {
-        expr1 = clone_expression(var->expr);
-      }
-      expr2 = new_expression(expchar,NULL);
-      exprcomb = compound_expr(expr1, expression_value(expr1, 2), "+", expr2, expression_value(expr2, 2), 0);
-      memcpy (var->expr, exprcomb, sizeof(*exprcomb));
-    }
-    else if (var->type==1){
-
-      char *result = malloc(100 * sizeof(char));
-      sprintf(result, "%.16f", var->value);
-      expr1 = new_expression(result,NULL);
-      free(result);
-      
-      expr2 = new_expression(expchar,NULL);
-      exprcomb = compound_expr(expr1, expression_value(expr1, 2), "+", expr2, expression_value(expr2, 2),0);
-      var->expr = mymalloc("add expression", sizeof *var->expr);
-      memcpy (var->expr, exprcomb, sizeof(*exprcomb));
-      var->type=2; //makes it an expression
-    }
-    else{
-      warning("Variable has to be declared as defered expression or as an assignment: ", varname);
-    }
-
+  else if(var->type==1 || (var->expr==NULL)) {
+      sprintf(tmp_var_expr, "%.16f", var->value);
+  }
+  else {
+    strcpy(tmp_var_expr, var->expr->string);
   }
-  else{
-    warning("The variable that trying to add expression to is not existing: ", varname);
+  strcat(in_string_tmp, tmp_var_expr);
+  
+  // Fine to only check the first because the string is already stripped. 
+  if(expchar[0]=='+' || expchar[0]=='-') {
+    strcat(in_string_tmp, " ");
   }
+  else { //If not a + or minus in the beginning then we add a +
+    strcat(in_string_tmp, " + ");
+  }
+
+  strcat(in_string_tmp, expchar);    
+  
+  strcat(in_string_tmp, ";");
+  pro_input(in_string_tmp);
+  return;
 }
 
 void
diff --git a/src/mad_var.c b/src/mad_var.c
index 48db37411..b70977411 100644
--- a/src/mad_var.c
+++ b/src/mad_var.c
@@ -351,7 +351,7 @@ enter_variable(struct in_cmd* cmd) /* stores variable contained in cmd */
   n = name = permbuff(cmd->tok_list->p[name_pos]);
   if (exp_type == 0)
   {
-    warning("illegal expression set to 0 in:",
+    warning("illegal expression, expression NOT updated for the following :",
             join_b(cmd->tok_list->p, cmd->tok_list->curr));
   }
   else
diff --git a/tests/test-addexpression/test-addexpression.ref b/tests/test-addexpression/test-addexpression.ref
index 2240f2678..609eb9434 100644
--- a/tests/test-addexpression/test-addexpression.ref
+++ b/tests/test-addexpression/test-addexpression.ref
@@ -1,9 +1,9 @@
 
   ++++++++++++++++++++++++++++++++++++++++++++
-  +     MAD-X 5.07.00  (64 bit, Linux)       +
+  +     MAD-X 5.09.01  (64 bit, Linux)       +
   + Support: mad@cern.ch, http://cern.ch/mad +
-  + Release   date: 2021.05.03               +
-  + Execution date: 2021.12.10 13:04:55      +
+  + Release   date: 2023.12.04               +
+  + Execution date: 2024.01.22 17:05:50      +
   ++++++++++++++++++++++++++++++++++++++++++++
 	
 
@@ -17,10 +17,13 @@ add2expr, var = x, expr=-a;
 
 add2expr, var = x, expr=b;
 
+++++++ info: x redefined
 add2expr, var = y, expr=b;
 
+++++++ info: y redefined
 add2expr, var = z, expr=c;
 
+++++++ info: z redefined
 
 
 z1=100; ! Doesn't change because not a defered expression
@@ -37,13 +40,13 @@ c=4;
 
 show, x;
 
-x                  := 0.0000000000000000 - a + b  ;
+x                  := -a+b               ;
 show, y;
 
-y                  := 2.0000000000000000 + b  ;
+y                  := 2.0000000000000000+b ;
 show, z;
 
-z                  := 0.0000000000000000 + c  ;
+z                  := 0.0000000000000000+c ;
 
 
 value, x;