diff --git a/draw/code_to_image_wrapper.py b/draw/code_to_image_wrapper.py
new file mode 100644
index 0000000..b65896f
--- /dev/null
+++ b/draw/code_to_image_wrapper.py
@@ -0,0 +1,13 @@
+import draw.code_to_image as cti
+
+class NSD_writer(object):
+    def __init__(self, filepath: str, x_sz: int, y_sz: int) -> None:
+        self.filepath = filepath
+        self.x_sz = x_sz
+        self.y_sz = y_sz
+    
+    def __enter__(self):
+        cti.NSD_init(self.x_sz, self.y_sz)
+    
+    def __exit__(self, _, __, ___):
+        cti.NSD_save(self.filepath)
\ No newline at end of file
diff --git a/interpreter/NassiShneidermann.py b/interpreter/NassiShneidermann.py
index fc21424..5c2cecf 100644
--- a/interpreter/NassiShneidermann.py
+++ b/interpreter/NassiShneidermann.py
@@ -3,7 +3,7 @@ import logging
 
 from draw.Iinstruction import Iinstruction
 from interpreter import interpret_source as itp
-from draw import code_to_image as cti
+from draw.code_to_image_wrapper import NSD_writer
 
 
 class NassiShneidermanDiagram:
@@ -29,15 +29,14 @@ class NassiShneidermanDiagram:
         return int(h)
 
     def convert_to_image(self, filename: str, x_size: int=200):
-        logging.info(f"Saving NSD to {filename}.png")
         image_y_sz = self.get_image_height()
-        cti.NSD_init(x_size, image_y_sz)
-        x, y = 0, 0
+        logging.info(f"Saving NSD to {filename}.png...")
+        with NSD_writer(filename, x_size, image_y_sz):
+            x, y = 0, 0
 
-        for instruction in self.instructions:
-            x, y = instruction.to_image(x, y, x_size)
-        
-        cti.NSD_save(filename)
+            for instruction in self.instructions:
+                x, y = instruction.to_image(x, y, x_size)
+            logging.info("Done!")
 
     def load_from_file(self, filepath:str):
         instructions = itp.load_instructions(filepath)
diff --git a/interpreter/interpret_source.py b/interpreter/interpret_source.py
index dadc40a..35c1c62 100644
--- a/interpreter/interpret_source.py
+++ b/interpreter/interpret_source.py
@@ -114,7 +114,7 @@ def handle_do_while(line: str, src: List[str], i: int) -> Tuple[Iinstruction, in
         bracket_index = end_line.rindex(')') #throws if contruct id ill-formed
         instruction_txt = end_line[7:bracket_index]
     elif check_line_start(src, i+1, "while("):
-        i += 1 #make sure we return the correct value for i
+        i += 1
         end_line = src[i]
         bracket_index = end_line.rindex(')')
         instruction_txt = end_line[6:bracket_index]
@@ -167,5 +167,5 @@ def load_instructions(filepath: str) -> List[Iinstruction]:
     src = load_src(filepath)
     instructions, i = get_instructions_in_scope(src)
     if i != len(src):
-        raise InterpreterError("Unknown error during source interpretation! Unsupported language constructs or ill-formed?")
+        raise InterpreterError("Unknown error during source interpretation! Unsupported language constructs or ill-formed source?")
     return instructions
\ No newline at end of file