diff --git a/.gitignore b/.gitignore
index 7fa8e3a..b0ee3e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,5 @@ __pycache__/
 res/output/
 res/input/
 .vscode/
-*.pyc
\ No newline at end of file
+*.pyc
+*.png
\ No newline at end of file
diff --git a/README.md b/README.md
index 53f0411..ad574ba 100644
--- a/README.md
+++ b/README.md
@@ -7,4 +7,4 @@ In the final version, you will just have to execute the nassi.exe and choose you
 
 Using:
 PySimpleGUI &
-Pillow
+Pillow
\ No newline at end of file
diff --git a/interpreter/NassiShneidermann.py b/interpreter/NassiShneidermann.py
index a352f40..86f0c60 100644
--- a/interpreter/NassiShneidermann.py
+++ b/interpreter/NassiShneidermann.py
@@ -24,7 +24,7 @@ class NassiShneidermanDiagram:
         self.instructions[instruction_key] = instruction
         logging.debug("added instruction %s : %s", instruction_key, instruction.instruction_text)
 
-    def convert_to_image(self, filename: str, x_size=200):
+    def convert_to_image(self, filename: str, x_size: int=200):
         logging.info(f"Saving NSD to {filename}.png")
         cti.NSD_init(x_size, 5000)
         x, y, x_sz = 0, 0, x_size