diff --git a/base/dict.jl b/base/dict.jl
index 22fd8a3a9f844..750b98ea070f2 100644
--- a/base/dict.jl
+++ b/base/dict.jl
@@ -359,7 +359,7 @@ end
 
 function setindex!(h::Dict{K,V}, v0, key0) where V where K
     key = convert(K, key0)
-    if !isequal(key, key0)
+    if !(isequal(key, key0)::Bool)
         throw(ArgumentError("$(limitrepr(key0)) is not a valid key for type $K"))
     end
     setindex!(h, v0, key)