diff --git a/src/convert/axisarray.jl b/src/convert/axisarray.jl
index cb147c5e..bc7e9f5e 100644
--- a/src/convert/axisarray.jl
+++ b/src/convert/axisarray.jl
@@ -4,7 +4,7 @@ function rcopy(::Type{AxisArray}, r::Ptr{S}) where {S<:VectorSxp}
     dnames = getattrib(r, Const.DimNamesSymbol)
     isnull(dnames) && error("r has no dimnames")
     dsym = rcopy(Array{Symbol}, getnames(dnames))
-    for i in 1:length(dsym)
+    for i in eachindex(dsym)
         if dsym[i] == Symbol("")
             dsym[i] = i == 1 ? (:row) : i == 2 ? (:col) : i == 3 ? (:page) : Symbol(:dim_, i)
         end
diff --git a/src/convert/base.jl b/src/convert/base.jl
index 2463cd4f..b14375a3 100644
--- a/src/convert/base.jl
+++ b/src/convert/base.jl
@@ -114,7 +114,7 @@ end
 function rcopy(::Type{Vector{Bool}},s::Ptr{LglSxp})
     a = Array{Bool}(undef, length(s))
     v = unsafe_vec(s)
-    for i = 1:length(a)
+    for i in eachindex(a, v)
         a[i] = v[i] != 0
     end
     a
@@ -122,7 +122,7 @@ end
 function rcopy(::Type{BitVector},s::Ptr{LglSxp})
     a = BitArray(undef, length(s))
     v = unsafe_vec(s)
-    for i = 1:length(a)
+    for i in eachindex(a, v)
         a[i] = v[i] != 0
     end
     a
@@ -135,7 +135,7 @@ end
 function rcopy(::Type{Array{Bool}},s::Ptr{LglSxp})
     a = Array{Bool}(undef, size(s)...)
     v = unsafe_vec(s)
-    for i = 1:length(a)
+    for i in eachindex(a, v)
         a[i] = v[i] != 0
     end
     a
@@ -143,7 +143,7 @@ end
 function rcopy(::Type{BitArray},s::Ptr{LglSxp})
     a = BitArray(undef, size(s)...)
     v = unsafe_vec(s)
-    for i = 1:length(a)
+    for i in eachindex(a, v)
         a[i] = v[i] != 0
     end
     a
@@ -264,8 +264,10 @@ sexp(::Type{RClass{:character}},st::AbstractString) = sexp(RClass{:character}, s
 function sexp(::Type{RClass{:character}}, a::AbstractArray{T}) where T<:AbstractString
     ra = protect(allocArray(StrSxp, size(a)...))
     try
-        for i in 1:length(a)
-            ra[i] = a[i]
+        # we want this to work even if a doesn't use one-based indexing
+        # we only care about ra having the same length (which it does)
+        for (i, idx) in zip(eachindex(ra), eachindex(a))
+            ra[i] = a[idx]
         end
     finally
         unprotect(1)
@@ -296,8 +298,10 @@ end
 function sexp(::Type{RClass{:list}}, a::AbstractArray)
     ra = protect(allocArray(VecSxp, size(a)...))
     try
-        for i in 1:length(a)
-            ra[i] = a[i]
+        # we want this to work even if a doesn't use one-based indexing
+        # we only care about ra having the same length (which it does)
+        for (i, idx) in zip(eachindex(ra), eachindex(a))
+            ra[i] = a[idx]
         end
     finally
         unprotect(1)
diff --git a/src/methods.jl b/src/methods.jl
index 2b5fbfab..6f3cbe17 100644
--- a/src/methods.jl
+++ b/src/methods.jl
@@ -99,6 +99,7 @@ function iterate(s::Ptr{S}, state) where S<:VectorSxp
     (s[state], state)
 end
 
+Base.eachindex(s::Ptr{<:VectorSxp}) = Base.OneTo(length(s))
 
 """
 Set element of a VectorSxp by a label.