diff --git a/spacy/errors.py b/spacy/errors.py
index 0f8091e3a..e7f59c091 100644
--- a/spacy/errors.py
+++ b/spacy/errors.py
@@ -212,7 +212,8 @@ class Warnings(metaclass=ErrorsWithCodes):
     # v4 warning strings
     W400 = ("`use_upper=False` is ignored, the upper layer is always enabled")
     W401 = ("`incl_prior is True`, but the selected knowledge base type {kb_type} doesn't support prior probability "
-            "lookups.")
+            "lookups (`.supports_prior_probs is False`). If your KB does support prior probability lookups, make sure "
+            "to return True in `.supports_prior_probs`.")
 
 
 class Errors(metaclass=ErrorsWithCodes):