diff --git a/apps/diaries/services.py b/apps/diaries/services.py
index aee6fe9..e4210dc 100644
--- a/apps/diaries/services.py
+++ b/apps/diaries/services.py
@@ -1,14 +1,26 @@
-from rp2.business_logic import XP_PER_DAIRY_COMMIT, MESSAGE_LENGTH_WHICH_BRINGS_XP_IN_DIARY_COMMIT
+from rp2.business_logic import (
+    XP_PER_DAIRY_COMMIT,
+    MESSAGE_LENGTH_WHICH_BRINGS_XP_IN_DIARY_COMMIT,
+    STAR_FILLING_BONUS_VALUE,
+    ADDITIONAL_XP_FOR_STAR_FILLING,
+)
 
 from .models import DiaryCommit
 
 
 def calculate_diary_commit_xp(commit: DiaryCommit):
-    additional_xp_for_more_detailed_message = int(
-        len(commit.message) / MESSAGE_LENGTH_WHICH_BRINGS_XP_IN_DIARY_COMMIT
-    )
     total_xp = [
         XP_PER_DAIRY_COMMIT,
-        additional_xp_for_more_detailed_message,
     ]
+
+    # additional xp for more detailed message
+    additional_xp_for_more_detailed_message = int(
+        len(commit.message) / MESSAGE_LENGTH_WHICH_BRINGS_XP_IN_DIARY_COMMIT
+    )
+    total_xp.append(additional_xp_for_more_detailed_message)
+
+    # additional xp for star filling bonus
+    if commit.diary.commits.count() == STAR_FILLING_BONUS_VALUE:
+        total_xp.append(ADDITIONAL_XP_FOR_STAR_FILLING)
+
     return sum(total_xp)
diff --git a/rp2/business_logic.py b/rp2/business_logic.py
index 6d22552..06faacf 100644
--- a/rp2/business_logic.py
+++ b/rp2/business_logic.py
@@ -3,6 +3,8 @@
 XP_PER_DAIRY_COMMIT = 5
 MESSAGE_LENGTH_WHICH_BRINGS_XP_IN_DIARY_COMMIT = 50
 LEVEL_STEP_THAT_CHANGE_COLOR_DESIGN = 3
+STAR_FILLING_BONUS_VALUE = 5
+ADDITIONAL_XP_FOR_STAR_FILLING = 28
 
 # ===== RULES
 COMMIT_MIN_LENGTH = 10