diff --git a/Makefile b/Makefile
index 11061ac..92b7bfa 100644
--- a/Makefile
+++ b/Makefile
@@ -32,6 +32,9 @@ build/utils/buffer.o: src/utils/buffer.c
 	@$(ECHO) "CC\t\t"$<
 	@$(CC) $(CFLAGS) $< -c -o $@ $(LIBS)
 
+run: all
+	@$(OUT) tests/program.pinky
+
 clean:
 	@$(ECHO) "Cleaning..."
 	@$(RM) -f $(FILES) $(OUT)
diff --git a/src/lexer.c b/src/lexer.c
index 83d6967..e1b284d 100644
--- a/src/lexer.c
+++ b/src/lexer.c
@@ -79,9 +79,7 @@ add_token (enum token_type type, struct lexer *l)
 	if (!l)
 		return;
 
-	unsigned int size = l->cur - l->start;
-	char *lexeme = calloc (size, sizeof (char));
-	strncpy (lexeme, buffer_get (l->source) + l->start, size);
+	char *lexeme = buffer_slice (l->start, l->cur, l->source);
 
 	vector_push_back (token_create_heap (type, l->line, lexeme), &l->tokens);
 	free (lexeme);
@@ -293,6 +291,9 @@ lexer_lex (struct lexer *l)
 				handle_string (c, l);
 			else if (isalpha (c) || c == '_')
 				handle_identifier (l);
+			else
+				fprintf (stderr, "lexer_lex: unexpected character `%c' at line %d\n",
+								 c, l->line);
 		}
 }
 
diff --git a/tests/program.pinky b/tests/program.pinky
index 2e4a792..423399f 100644
--- a/tests/program.pinky
+++ b/tests/program.pinky
@@ -1,7 +1,7 @@
 -- initialise variables
 pi := 3.141592
 
-x := 8.23
+x := 8.23 - -3.5
 
 if x >= 0 then
 	println ("x is positive")