diff --git a/src/math_parser_diag.cpp b/src/math_parser_diag.cpp
index 9c72fe8d677d7..142a659be845b 100644
--- a/src/math_parser_diag.cpp
+++ b/src/math_parser_diag.cpp
@@ -274,7 +274,7 @@ diag_eval_dbl_f faction_food_supply_eval( char /* scope */,
     return [fac_val = params[0], vit_val]( const_dialogue const & d ) {
         faction *fac = g->faction_manager_ptr->get( faction_id( fac_val.str( d ) ) );
         if( !vit_val.is_empty() ) {
-            return static_cast<double>( fac->food_supply.get_vitamin( vitamin_id( vit_val.str() ) ) );
+            return static_cast<double>( fac->food_supply.get_vitamin( vitamin_id( vit_val.str( d ) ) ) );
         }
         return static_cast<double>( fac->food_supply.calories );
     };
@@ -287,7 +287,7 @@ diag_assign_dbl_f faction_food_supply_ass( char /* scope */,
     return [fac_val = params[0], vit_val]( dialogue const & d, double val ) {
         faction *fac = g->faction_manager_ptr->get( faction_id( fac_val.str( d ) ) );
         if( !vit_val.is_empty() ) {
-            fac->food_supply.add_vitamin( vitamin_id( vit_val.str() ), val );
+            fac->food_supply.add_vitamin( vitamin_id( vit_val.str( d ) ), val );
             return;
         }
         fac->food_supply.calories = val;