diff --git a/relational/optimizations.py b/relational/optimizations.py
index 51819a7..d9f15e2 100644
--- a/relational/optimizations.py
+++ b/relational/optimizations.py
@@ -72,7 +72,7 @@ def duplicated_select(n: parser.Node) -> Tuple[parser.Node, int]:
     in and
     '''
     changes = 0
-    while n.name == SELECTION and n.child.name == SELECTION:
+    while isinstance(n, parser.UNARY) and n.name == SELECTION and isinstance(n.child, parser.UNARY) and n.child.name == SELECTION:
         changes += 1
         prop = n.prop
 
@@ -147,7 +147,7 @@ def down_to_unions_subtractions_intersections(n: parser.Node) -> Tuple[parser.No
     '''
     changes = 0
     _o = (UNION, DIFFERENCE, INTERSECTION)
-    if n.name == SELECTION and n.child.name in _o:
+    if isinstance(n, parser.UNARY) and n.name == SELECTION and n.child.name in _o:
         l = parser.Unary(SELECTION, n.prop, n.child.left)
         r = parser.Unary(SELECTION, n.prop, n.child.right)
 
@@ -170,7 +170,7 @@ def duplicated_projection(n: parser.Node) -> Tuple[parser.Node, int]:
 def selection_inside_projection(n: parser.Node) -> Tuple[parser.Node, int]:
     '''This function locates things like  σ j (π k(R)) and
     converts them into π k(σ j (R))'''
-    if n.name == SELECTION and n.child.name == PROJECTION:
+    if isinstance(n, parser.UNARY) and n.name == SELECTION and n.child.name == PROJECTION:
         child = parser.Unary(
             SELECTION,
             n.prop,
@@ -338,7 +338,7 @@ def swap_rename_select(n: parser.Node) -> int:
     Renaming the attributes used in the
     selection, so the operation is still valid.'''
 
-    if n.name == SELECTION and n.child.name == RENAME:
+    if isinstance(n, parser.UNARY) and n.name == SELECTION and n.child.name == RENAME:
         # This is an inverse mapping for the rename
         renames = {v: k for k, v in n.child.get_rename_prop().items()}
 
@@ -438,7 +438,7 @@ def selection_and_product(n: parser.Node, rels: Dict[str, Relation]) -> parser.N
     σ l (σ j (R) * σ i (Q)). Where j contains only attributes belonging to R,
     i contains attributes belonging to Q and l contains attributes belonging to both'''
 
-    if n.name == SELECTION and n.child.name in (PRODUCT, JOIN):
+    if isinstance(n, parser.UNARY) and n.name == SELECTION and n.child.name in (PRODUCT, JOIN):
         l_attr = n.child.left.result_format(rels)
         r_attr = n.child.right.result_format(rels)