diff --git a/base/mmap.jl b/base/mmap.jl
index 0477ea8482686..5f9cda44f0fe2 100644
--- a/base/mmap.jl
+++ b/base/mmap.jl
@@ -204,9 +204,11 @@ const MS_INVALIDATE = 2
 const MS_SYNC = 4
 
 function sync!{T}(m::Array{T}, flags::Integer=MS_SYNC)
-    @unix_only systemerror("msync", ccall(:msync, Cint, (Ptr{Void}, Csize_t, Cint), pointer(m), length(m)*sizeof(T), flags) != 0)
+    offset = rem(UInt(pointer(m)), PAGESIZE)
+    ptr = pointer(m) - offset
+    @unix_only systemerror("msync", ccall(:msync, Cint, (Ptr{Void}, Csize_t, Cint), ptr, length(m)*sizeof(T), flags) != 0)
     @windows_only systemerror("could not FlushViewOfFile: $(Libc.FormatMessage())",
-                    ccall(:FlushViewOfFile, stdcall, Cint, (Ptr{Void}, Csize_t), pointer(m), length(m)) == 0)
+                    ccall(:FlushViewOfFile, stdcall, Cint, (Ptr{Void}, Csize_t), ptr, length(m)) == 0)
 end
 sync!(B::BitArray, flags::Integer=MS_SYNC) = sync!(B.chunks, flags)
 
diff --git a/test/mmap.jl b/test/mmap.jl
index 0cbb56d3dad33..b378427890926 100644
--- a/test/mmap.jl
+++ b/test/mmap.jl
@@ -278,3 +278,16 @@ n = similar(m, 12)
 @test length(n) == 12
 @test size(n) == (12,)
 finalize(m); m = nothing; gc()
+
+# test #14885
+file = tempname()
+touch(file)
+open(file, "r+") do s
+    A = Mmap.mmap(s, Vector{UInt8}, (10,), 0);
+    Mmap.sync!(A)
+    finalize(A); A = nothing; gc()
+    A = Mmap.mmap(s, Vector{UInt8}, (10,), 1);
+    Mmap.sync!(A)
+    finalize(A); A = nothing; gc()
+end
+rm(file)