diff --git a/Project.toml b/Project.toml
index 7ffbf3b..79f404f 100644
--- a/Project.toml
+++ b/Project.toml
@@ -2,7 +2,7 @@ name = "Azure"
 uuid = "34b51195-c7f2-5807-8107-6ca017e2682c"
 keywords = ["azure", "cloud", "api", "julia"]
 desc = "Julia interface to Azure APIs"
-version = "0.4.0"
+version = "0.4.1"
 
 [deps]
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
@@ -10,6 +10,7 @@ Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 Downloads = "f43a241f-c20a-4ad4-852c-f6b1247861c6"
 JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 MbedTLS = "739be429-bea8-5141-9913-cc70e7f3736d"
+Mmap = "a63ad114-7e13-5084-954f-fe012c677804"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Swagger = "2d69052b-6a58-5cd9-a030-a48559c324ac"
 XMLDict = "228000da-037f-5747-90a9-8195ccbf91a5"
diff --git a/src/StorageServices/StorageServices.jl b/src/StorageServices/StorageServices.jl
index ab7c9f4..b997ce4 100644
--- a/src/StorageServices/StorageServices.jl
+++ b/src/StorageServices/StorageServices.jl
@@ -8,6 +8,7 @@ using URIs
 using MbedTLS
 using Dates
 using Base64
+using Mmap
 
 include("common.jl")
 include("blob.jl")
diff --git a/src/StorageServices/blob.jl b/src/StorageServices/blob.jl
index f389cb3..0eb5288 100644
--- a/src/StorageServices/blob.jl
+++ b/src/StorageServices/blob.jl
@@ -107,6 +107,19 @@ end
 
 const valid_blob_types = ("BlockBlob", "PageBlob", "AppendBlob")
 
+function check_mappable_file(io)
+    if isa(io, IOStream)
+        try
+            fsz = filesize(io)
+            data = Mmap.mmap(io, Vector{UInt8}, fsz)
+            return IOBuffer(data), fsz
+        catch
+            return io, nothing
+        end
+    end
+    return io, nothing
+end
+
 """
 Creates a new block, page, or append blob, or updates the content of an existing block blob.
 
@@ -164,8 +177,22 @@ function putBlob(ctx, subscription_id::String, resource_group_name::String, uri:
                     content_length = length(codeunits(block_blob_contents))
                 elseif isa(block_blob_contents, Vector{UInt8})
                     content_length = length(block_blob_contents)
+                elseif isa(block_blob_contents, IOBuffer)
+                    content_length = block_blob_contents.size
+                else
+                    wrapped_contents, content_length = check_mappable_file(block_blob_contents)
+                    if content_length === nothing
+                        error("content_length must be specified for blob contents of type $(typeof(block_blob_contents))")
+                    else
+                        block_blob_contents = wrapped_contents
+                    end
+                end
+            elseif isa(block_blob_contents, IOStream)
+                wrapped_contents, wrapped_content_length = check_mappable_file(block_blob_contents)
+                if content_length !== wrapped_content_length
+                    error("content_length must match the length of the stream")
                 else
-                    error("content_length must be specified for blob contents of type $(typeof(block_blob_contents))")
+                    block_blob_contents = wrapped_contents
                 end
             end
         end