diff --git a/src/Rings/mpoly-localizations.jl b/src/Rings/mpoly-localizations.jl
index 17dcfe69810a..50ac5e63ad3e 100644
--- a/src/Rings/mpoly-localizations.jl
+++ b/src/Rings/mpoly-localizations.jl
@@ -534,6 +534,8 @@ function ==(T::AbsMPolyMultSet, U::AbsMPolyMultSet)
 end
 
 function Base.hash(T::AbsMPolyMultSet, h::UInt)
+  @warn """Hashing of multiplicative sets of type AbsMPolyMultSet is badly implemented 
+  and should not be used. Please provide a better implementation for the type $(typeof(T))."""
   b = 0x7ce51a28c47ec5e1 % UInt
   h = hash(typeof(T), h)
   h = hash(ambient_ring(T), h)