diff --git a/src/psyclone/psyir/nodes/acc_directives.py b/src/psyclone/psyir/nodes/acc_directives.py
index b765517be4e..50c3e421086 100644
--- a/src/psyclone/psyir/nodes/acc_directives.py
+++ b/src/psyclone/psyir/nodes/acc_directives.py
@@ -276,14 +276,14 @@ def begin_string(self):
         sym_list = _sig_set_to_string(self._sig_set)
 
         # options
-        options = f" copyin({sym_list}"
+        options = f" copyin({sym_list})"
 
         # async
         options += _build_async_string(self._async_queue)
 
         # Variables need lexicographic sorting since sets guarantee no ordering
         # and members of composite variables must appear later in deep copies.
-        return f"acc enter data{options})"
+        return f"acc enter data{options}"
 
     def data_on_device(self, parent):
         '''
diff --git a/src/psyclone/transformations.py b/src/psyclone/transformations.py
index 6426a68fee2..333ec672a90 100644
--- a/src/psyclone/transformations.py
+++ b/src/psyclone/transformations.py
@@ -2284,9 +2284,9 @@ def apply(self, sched, options=None):
             posn = sched.children.index(current)
 
         # handle async option
-        async_queue = None
-        if options != None:
-            async_queue = options.get('async_queue', False)
+        if options == None:
+            options = {}
+        async_queue = options.get('async_queue', False)
 
         # Add the directive at the position determined above, i.e. just before
         # the first statemement containing an OpenACC compute construct.
@@ -2322,17 +2322,17 @@ def validate(self, sched, options=None):
                                       "region - cannot add an enter data.")
 
         # do not has mixed async
-        async_queue = None
-        if options != None:
-            async_queue = options.get('async_queue', False)
-        if async_queue != False:
+        if options == None:
+            options = {}
+        async_queue = options.get('async_queue', False)
+        if async_queue:
             directive_cls = (ACCKernelsDirective, ACCParallelDirective)
             for directive in sched.walk(directive_cls):
-                if directive.async_queue != False and directive.async_queue != async_queue:
+                if directive.async_queue and directive.async_queue != async_queue:
                     raise TransformationError(f"Tried to apply async() while another one is used internally \
                                                with different queue ({async_queue} != {directive.async_queue}) !")
             directive = sched.ancestor(directive_cls)
-            if directive and directive.async_queue != False and directive.async_queue != async_queue:
+            if directive and directive.async_queue and directive.async_queue != async_queue:
                 raise TransformationError(f"Tried to apply async() while another one is used in ancestor \
                                             with different queue ({async_queue} != {directive.async_queue}) !")
 
@@ -2570,17 +2570,17 @@ def validate(self, nodes, options):
                 "array range but none were found.")
 
         # do not has mixed async
-        async_queue = None
-        if options != None:
-            async_queue = options.get('async_queue', False)
-        if async_queue != False:
+        if options == None:
+            options = {}
+        async_queue = options.get('async_queue', False)
+        if async_queue:
             directive_cls = (ACCKernelsDirective, ACCParallelDirective)
             for directive in sched.walk(directive_cls):
                 if directive.async_queue != False and directive.async_queue != async_queue:
                     raise TransformationError(f"Tried to apply async() while another one is used internally \
                                                with different queue ({async_queue} != {directive.async_queue}) !")
             directive = sched.ancestor(directive_cls)
-            if directive and directive.async_queue != False and directive.async_queue != async_queue:
+            if directive and directive.async_queue and directive.async_queue != async_queue:
                 raise TransformationError(f"Tried to apply async() while another one is used in ancestor \
                                             with different queue ({async_queue} != {directive.async_queue}) !")