diff --git a/base/string.jl b/base/string.jl
index 111dd433aefd3..07100f2b1d3a4 100644
--- a/base/string.jl
+++ b/base/string.jl
@@ -661,7 +661,7 @@ const memhash_seed = UInt === UInt64 ? 0x71e729fd56419c81 : 0x56419c81
 
 function hash{T<:ByteString}(s::Union(T,SubString{T}), h::UInt)
     h += memhash_seed
-    ccall(memhash, UInt, (Ptr{UInt8}, Csize_t, UInt32), s, sizeof(s), h % UInt32) + h
+    ccall(memhash, UInt, (Ptr{UInt8}, Csize_t, UInt32), pointer(s), sizeof(s), h % UInt32) + h
 end
 hash(s::AbstractString, h::UInt) = hash(bytestring(s), h)