diff --git a/TODO b/TODO
index 8dbe58e2f1c6863012de58c2868333db041c4345..b458f92fb10bc4945aa6f7072f0692e317a91c0e 100644
--- a/TODO
+++ b/TODO
@@ -111,3 +111,5 @@ Division of 0 by 1 reduces to 0.
  - MESSAGES needs to be expanded.
 
  - Use pretty-print for expressions in hint messages.
+
+ - Parser: add unit tests for operator associativity (derivatives/integrals).
diff --git a/src/parser.py b/src/parser.py
index a2ced27c96d0a9366c6d4442c2f4e5efcfac75ef..05114c514bd5a4788ed21a01ae004b984508e072 100644
--- a/src/parser.py
+++ b/src/parser.py
@@ -86,7 +86,7 @@ class Parser(BisonParser):
     # ------------------------------
     precedences = (
         ('left', ('COMMA', )),
-        ('right', ('INTEGRAL', 'DERIVATIVE')),
+        ('left', ('INTEGRAL', 'DERIVATIVE')),
         ('left', ('OR', )),
         ('left', ('AND', )),
         ('left', ('EQ', )),