diff --git a/src/clientlayers/ConnectionRequest.jl b/src/clientlayers/ConnectionRequest.jl
index b91febfe..23881bf9 100644
--- a/src/clientlayers/ConnectionRequest.jl
+++ b/src/clientlayers/ConnectionRequest.jl
@@ -110,7 +110,8 @@ function connectionlayer(handler)
                     return r
                 end
                 if target_url.scheme in ("https", "wss")
-                    io = Connections.sslupgrade(socket_type_tls, io, target_url.host; readtimeout=readtimeout, kw...)
+                    InnerIOType = sockettype(target_url, socket_type, socket_type_tls, get(kw, :sslconfig, nothing))
+                    io = Connections.sslupgrade(InnerIOType, io, target_url.host; readtimeout=readtimeout, kw...)
                 end
                 req.headers = filter(x->x.first != "Proxy-Authorization", req.headers)
             end
diff --git a/test/client.jl b/test/client.jl
index 2b6e32ba..ad76ad9f 100644
--- a/test/client.jl
+++ b/test/client.jl
@@ -33,6 +33,36 @@ end
     @test_throws ArgumentError HTTP.get("https://$httpbin/ip", sslconfig=MbedTLS.SSLConfig(false), socket_type_tls=OpenSSL.SSLStream)
 end
 
+@testset "issue 1172" begin
+    # Connections through a proxy need to choose an IOType twice rather than
+    # just once.
+    # https://github.com/JuliaWeb/HTTP.jl/issues/1172
+
+    # This proxy accepts two requests, ignoring the content of the request and
+    # returning 200 each time.
+    proxy = listen(IPv4(0), 8082)
+    try
+        @async begin
+            sock = accept(proxy)
+            while isopen(sock)
+                line = readline(sock)
+                @show 1, line
+                isempty(line) && break
+            end
+            write(sock, "HTTP/1.1 200\r\n\r\n")
+            # Test that we receive something that looks like a client hello
+            # (indicating that we tried to upgrade the connection to TLS)
+            line = readline(sock)
+            @test startswith(line, "\x16")
+        end
+
+        @test_throws HTTP.RequestError HTTP.head("https://$httpbin.com"; proxy="http://localhost:8082", readtimeout=1, retry=false)
+    finally
+        close(proxy)
+        HTTP.Connections.closeall()
+    end
+end
+
 @testset "@client macro" begin
     @eval module MyClient
         using HTTP