diff --git a/c/allergies/src/allergies.c b/c/allergies/src/allergies.c
index 9a879ae..d469726 100644
--- a/c/allergies/src/allergies.c
+++ b/c/allergies/src/allergies.c
@@ -1,9 +1,11 @@
 #include "allergies.h"
 
+#ifdef USE_ALLERGIC_TO_FUNCTION
 bool is_allergic_to(const allergen_t all, const uint32_t val)
 {
     return !!(val & (1 << all));
 }
+#endif
 
 allergen_list_t get_allergens(uint32_t val)
 {
diff --git a/c/allergies/src/allergies.h b/c/allergies/src/allergies.h
index bb42ebb..5a8e122 100644
--- a/c/allergies/src/allergies.h
+++ b/c/allergies/src/allergies.h
@@ -21,9 +21,13 @@ typedef struct {
    bool allergens[ALLERGEN_COUNT];
 } allergen_list_t;
 
-// We could use macro...
-// #define is_allergic_to(allerg, val) (!!((val) & (1 << (allerg))))
+// We can choose macro or function
+#ifdef USE_ALLERGIC_TO_FUNCTION
 bool is_allergic_to(const allergen_t allergen, const uint32_t value);
+#else
+#define is_allergic_to(allerg, val) (!!((val) & (1 << (allerg))))
+#endif
+
 allergen_list_t get_allergens(uint32_t value);
 
 /* See GNUmakefile below for explanation
diff --git a/c/templates/ex.h b/c/templates/ex.h
index 3c82085..7517664 100644
--- a/c/templates/ex.h
+++ b/c/templates/ex.h
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #endif
+
 #ifdef  TESTALL
 #undef  TEST_IGNORE
 #define TEST_IGNORE() {}