diff --git a/src/header.jl b/src/header.jl
index 1763033..c88bd01 100644
--- a/src/header.jl
+++ b/src/header.jl
@@ -1,6 +1,5 @@
 struct FITHeader
     sz::UInt8
-using Base: sizeof_ios_t
     protocol::UInt8
     version::AbstractVector{<:Real}
     size::Real