diff --git a/WDL/_parser.py b/WDL/_parser.py
index e9881eaf..ba9f3770 100644
--- a/WDL/_parser.py
+++ b/WDL/_parser.py
@@ -138,7 +138,7 @@
 ?expr_core: "(" expr ")"
           | literal
           | string
-          | "!" expr -> negate
+          | "!" expr_core -> negate
 
           | "[" [expr ("," expr)*] ","? "]" -> array
           | expr_core "[" expr "]" -> at
diff --git a/tests/test_0eval.py b/tests/test_0eval.py
index 2dcdee32..1f6c00b6 100644
--- a/tests/test_0eval.py
+++ b/tests/test_0eval.py
@@ -131,7 +131,10 @@ def test_logic(self):
             ("!!true", "true"),
             ("!false", "true"),
             ("!false && true", "true"),
-            ("!(false && true)", "true")
+            ("!false && false", "false"),
+            ("!true && false", "false"),
+            ("!(false && false)", "true"),
+            ("!(false && true)", "true"),
         )
 
     def test_arithmetic(self):