diff --git a/shared/sx/ref/bootstrap_py.py b/shared/sx/ref/bootstrap_py.py
index 87ecba2..af8d831 100644
--- a/shared/sx/ref/bootstrap_py.py
+++ b/shared/sx/ref/bootstrap_py.py
@@ -1647,10 +1647,17 @@ def _sx_parse_int(v, default=0):
         return default
 
 def is_primitive(name):
-    return name in PRIMITIVES
+    if name in PRIMITIVES:
+        return True
+    from shared.sx.primitives import get_primitive as _ext_get
+    return _ext_get(name) is not None
 
 def get_primitive(name):
-    return PRIMITIVES.get(name)
+    p = PRIMITIVES.get(name)
+    if p is not None:
+        return p
+    from shared.sx.primitives import get_primitive as _ext_get
+    return _ext_get(name)
 
 # Higher-order helpers used by transpiled code
 def map(fn, coll):
diff --git a/shared/sx/ref/sx_ref.py b/shared/sx/ref/sx_ref.py
index a11f98e..a8f3eb8 100644
--- a/shared/sx/ref/sx_ref.py
+++ b/shared/sx/ref/sx_ref.py
@@ -775,10 +775,17 @@ def _sx_parse_int(v, default=0):
         return default
 
 def is_primitive(name):
-    return name in PRIMITIVES
+    if name in PRIMITIVES:
+        return True
+    from shared.sx.primitives import get_primitive as _ext_get
+    return _ext_get(name) is not None
 
 def get_primitive(name):
-    return PRIMITIVES.get(name)
+    p = PRIMITIVES.get(name)
+    if p is not None:
+        return p
+    from shared.sx.primitives import get_primitive as _ext_get
+    return _ext_get(name)
 
 # Higher-order helpers used by transpiled code
 def map(fn, coll):