diff --git a/types.peg b/types.peg
index 64b78ee..037f149 100644
--- a/types.peg
+++ b/types.peg
@@ -146,7 +146,7 @@ class_class_member <-
     }
 
 class_instance_method <- p:proc_stmt {
-    assert(auxil->stack->mark = CLASS_BODY);
+    assert(auxil->stack->mark == CLASS_BODY);
     cst_nClass* cls = cst_NODECAST((cst_Node*)auxil->stack->data, Class);
     cls->members = realloc(cls->members, (++cls->n_members) * sizeof(cst_nClass_Member));
     cls->members[cls->n_members-1] = malloc(sizeof(cst_nClass_Member));
@@ -156,7 +156,7 @@ class_instance_method <- p:proc_stmt {
     cls->members[cls->n_members-1]->method = p;
 }
 class_class_method <- p:proc_stmt {
-    assert(auxil->stack->mark = CLASS_BODY);
+    assert(auxil->stack->mark == CLASS_BODY);
     cst_nClass* cls = cst_NODECAST((cst_Node*)auxil->stack->data, Class);
     cls->members = realloc(cls->members, (++cls->n_members) * sizeof(cst_nClass_Member));
     cls->members[cls->n_members-1] = malloc(sizeof(cst_nClass_Member));