diff --git a/lib/faraday/options/proxy_options.rb b/lib/faraday/options/proxy_options.rb
index c91dfc8d2..f94fe5745 100644
--- a/lib/faraday/options/proxy_options.rb
+++ b/lib/faraday/options/proxy_options.rb
@@ -11,6 +11,9 @@ class ProxyOptions < Options.new(:uri, :user, :password)
     def self.from(value)
       case value
       when String
+        # URIs without a scheme should default to http (like 'example:123').
+        # This fixes #1282 and prevents a silent failure in some adapters.
+        value = "http://#{value}" unless value.include?('://')
         value = { uri: Utils.URI(value) }
       when URI
         value = { uri: value }
@@ -19,6 +22,7 @@ def self.from(value)
           value[:uri] = Utils.URI(uri)
         end
       end
+
       super(value)
     end
 
diff --git a/spec/faraday/options/proxy_options_spec.rb b/spec/faraday/options/proxy_options_spec.rb
index a64ef0e27..7951554b8 100644
--- a/spec/faraday/options/proxy_options_spec.rb
+++ b/spec/faraday/options/proxy_options_spec.rb
@@ -14,6 +14,13 @@
       expect(options.inspect).to match('#<Faraday::ProxyOptions uri=')
     end
 
+    it 'defaults to http' do
+      options = Faraday::ProxyOptions.from 'example.org'
+      expect(options.port).to eq(80)
+      expect(options.host).to eq('example.org')
+      expect(options.scheme).to eq('http')
+    end
+
     it 'works with nil' do
       options = Faraday::ProxyOptions.from nil
       expect(options).to be_a_kind_of(Faraday::ProxyOptions)