diff --git a/src/info_zip.jl b/src/info_zip.jl
index 72c7bfb..7dc8d1f 100644
--- a/src/info_zip.jl
+++ b/src/info_zip.jl
@@ -80,6 +80,8 @@ end
 
 function Base.get(z::Archive, filename::AbstractString, default=nothing)
 
+    @assert !ismatch(r"^/", filename)
+
     if !haskey(z, filename)
         return default
     end
@@ -99,6 +101,8 @@ end
 
 function Base.setindex!(z::Archive, data, filename::AbstractString)
 
+    @assert !ismatch(r"^/", filename)
+
     # Write file to tempdir...
     mkpath(joinpath(z.tempdir, dirname(filename)))
     write(joinpath(z.tempdir, filename), data)