diff --git a/Data/Vector/Mutable.hs b/Data/Vector/Mutable.hs
index f346bc00fa9b7aefa3e204e37389af2ac284da92..88918894e2128b6edd8e7235c54831dde469ad3d 100644
--- a/Data/Vector/Mutable.hs
+++ b/Data/Vector/Mutable.hs
@@ -193,7 +193,7 @@ loopM !n k = let
   in go 0
 
 uninitialised :: a
-uninitialised = error "Data.Vector.Mutable: uninitialised element"
+uninitialised = error "Data.Vector.Mutable: uninitialised element. If you are trying to compact a vector, use the 'force' function to remove uninitialised elements from the underlying array."
 
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