diff --git a/include/util.h b/include/util.h
index d8c8fb6..81bdcb3 100644
--- a/include/util.h
+++ b/include/util.h
@@ -22,8 +22,8 @@
 #include <unistd.h>
 
 
-/* Parameter 'n' must not be in parentheses! */
-#define OT_TEXT_MAP_SIZE(p,n)   (sizeof(text_map->p) * text_map->size * n)
+/* Parameter 'p' must not be in parentheses! */
+#define OT_TEXT_MAP_SIZE(p,n)   (sizeof(text_map->p) * (text_map->size + (n)))
 
 
 extern otc_ext_malloc_t otc_ext_malloc;
diff --git a/src/util.cpp b/src/util.cpp
index f402ef1..c9c6405 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -133,21 +133,21 @@ int otc_text_map_add(struct otc_text_map *text_map, const char *key, size_t key_
 	if (text_map->count >= text_map->size) {
 		typeof(text_map->key)   ptr_key;
 		typeof(text_map->value) ptr_value;
+		size_t                  size_add = (text_map->size > 1) ? (text_map->size / 2) : 1;
 
-		if ((ptr_key = OT_CAST_TYPEOF(ptr_key, OTC_DBG_REALLOC(text_map->key, OT_TEXT_MAP_SIZE(key, 3 / 2)))) == nullptr)
+		if ((ptr_key = OT_CAST_TYPEOF(ptr_key, OTC_DBG_REALLOC(text_map->key, OT_TEXT_MAP_SIZE(key, size_add)))) == nullptr)
 			return retval;
 
 		text_map->key = ptr_key;
-		(void)memset(text_map->key + text_map->size, 0, OT_TEXT_MAP_SIZE(key, 1 / 2));
+		(void)memset(text_map->key + OT_TEXT_MAP_SIZE(key, 0), 0, sizeof(*(text_map->key)) * size_add);
 
-		if ((ptr_value = OT_CAST_TYPEOF(ptr_value, OTC_DBG_REALLOC(text_map->value, OT_TEXT_MAP_SIZE(value, 3 / 2)))) == nullptr)
+		if ((ptr_value = OT_CAST_TYPEOF(ptr_value, OTC_DBG_REALLOC(text_map->value, OT_TEXT_MAP_SIZE(value, size_add)))) == nullptr)
 			return retval;
 
 		text_map->value = ptr_value;
-		(void)memset(text_map->value + text_map->size, 0, OT_TEXT_MAP_SIZE(value, 1 / 2));
+		(void)memset(text_map->value + OT_TEXT_MAP_SIZE(value, 0), 0, sizeof(*(text_map->value)) * size_add);
 
-		/* Asignment operator '*=' should not be used here! */
-		text_map->size = text_map->size * 3 / 2;
+		text_map->size += size_add;
 	}
 
 	text_map->key[text_map->count]   = (flags & OTC_TEXT_MAP_DUP_KEY) ? ((key_len > 0) ? OTC_DBG_STRNDUP(key, key_len) : OTC_DBG_STRDUP(key)) : OT_CAST_CONST(char *, key);