diff --git a/src/parser/grammar_basic.c b/src/parser/grammar_basic.c
index b90cf68..b7f74c0 100644
--- a/src/parser/grammar_basic.c
+++ b/src/parser/grammar_basic.c
@@ -9,7 +9,7 @@
 
 // === Static functions
 
-enum ast_and_or_type and_or_tok_to_ast(enum token_type tok_type)
+static enum ast_and_or_type and_or_tok_to_ast(enum token_type tok_type)
 {
     switch (tok_type)
     {
@@ -47,7 +47,7 @@ struct ast *parse_list(struct lexer_context *ctx)
         if (current_node == NULL)
         {
             // TODO free list
-            //  There must be a function for that
+            // There must be a function for that
             return NULL;
         }
         result_list = list_append(result_list, current_node);
@@ -64,29 +64,35 @@ struct ast *parse_and_or(struct lexer_context *ctx)
 
     if (token->type == TOKEN_AND || token->type == TOKEN_OR)
     {
-        // set left part
+        // Set left part
 
         struct ast *left = result;
 
         // eat and_or token
         token = POP_TOKEN();
 
-        // set type
+        // Set type
         enum ast_and_or_type type = and_or_tok_to_ast(token->type);
 
         token = PEEK_TOKEN();
 
-        // skip newlines
+        // Skip newlines
         while (token->type == TOKEN_NEWLINE)
         {
             token = POP_TOKEN();
             token = PEEK_TOKEN();
         }
 
-        // right part
+        // Right part
         struct ast *right = parse_pipeline(ctx);
 
         result = ast_create_and_or(left, right, type);
+        if (result == NULL)
+        {
+            ast_free(&left);
+            ast_free(&right);
+            return NULL;
+        }
     }
 
     return result;
@@ -204,6 +210,7 @@ struct ast *parse_if_rule(struct lexer_context *ctx)
         return NULL;
     }
 
+    // Fi keyword
     token = POP_TOKEN();
     if (token->type != TOKEN_FI)
     {
@@ -214,6 +221,7 @@ struct ast *parse_if_rule(struct lexer_context *ctx)
         return NULL;
     }
 
+    // Result
     struct ast *result =
         ast_create_if(condition_content, then_content, else_content);
     if (result == NULL)
@@ -241,7 +249,7 @@ struct ast *parse_compound_list(struct lexer_context *ctx)
         token = PEEK_TOKEN();
     }
 
-    // and_or
+    // And/or
     current_cmd = parse_and_or(ctx);
     if (current_cmd == NULL)
         return NULL;
@@ -261,7 +269,7 @@ struct ast *parse_compound_list(struct lexer_context *ctx)
             token = PEEK_TOKEN();
         }
 
-        // and_or
+        // And/or
         current_cmd = parse_and_or(ctx);
         if (current_cmd == NULL)
             return NULL;
@@ -299,7 +307,7 @@ struct ast *parse_else_clause(struct lexer_context *ctx)
         token = POP_TOKEN();
         struct ast *condition = parse_compound_list(ctx);
 
-        // 'then'
+        // Then keyword
         token = POP_TOKEN();
         if (token->type != TOKEN_THEN)
         {
diff --git a/src/parser/grammar_basic.h b/src/parser/grammar_basic.h
index 0990e1b..840f05d 100644
--- a/src/parser/grammar_basic.h
+++ b/src/parser/grammar_basic.h
@@ -15,7 +15,7 @@ struct ast *parse_list(struct lexer_context *ctx);
 
 /* @brief Only parses a pipeline rule for the moment
  *
- * @code and_or = pipeline ;
+ * @code and_or = pipeline { ( '&&' | '||' ) {'\n'} pipeline } ;
  */
 struct ast *parse_and_or(struct lexer_context *ctx);
 
diff --git a/src/utils/ast/ast.c b/src/utils/ast/ast.c
index e336a73..75e1e7f 100644
--- a/src/utils/ast/ast.c
+++ b/src/utils/ast/ast.c
@@ -10,7 +10,7 @@
 
 void ast_free(struct ast **node)
 {
-    if (*node == NULL)
+    if (node == NULL || *node == NULL)
         return;
     // ast void does not need to be freed.
     if (ast_is_if(*node))