diff --git a/spec/integration/qt.cpp b/spec/integration/qt.cpp
index 1ab7a4a..5d3b7cb 100644
--- a/spec/integration/qt.cpp
+++ b/spec/integration/qt.cpp
@@ -20,6 +20,21 @@ struct QObject {
   }
 };
 
+// Test object conversion at Proc boundaries
+struct Conv {
+};
+
+struct ConvCpp {
+};
+
+ConvCpp conv_from_cpp(const Conv &) {
+  return { };
+}
+
+Conv conv_to_cpp(const ConvCpp &) {
+  return { };
+}
+
 // On to the actual test classes:
 
 // Tests signal/slots connection wrapping
@@ -27,6 +42,7 @@ class SomeObject {
   Q_OBJECT
 public:
   int normalMethod() { return 1; }
+  Conv convMethod() { return { }; }
 
 signals:
   void stuffHappened() {
@@ -48,6 +64,10 @@ class SomeObject {
   void privateSignal(QPrivateSignal) {
     // Empty.
   }
+
+  void convSignal(const Conv &) {
+    // Empty.
+  }
 };
 
 // Tests Q_GADGET cleaning
diff --git a/spec/integration/qt.yml b/spec/integration/qt.yml
index 14709f3..adf22ae 100644
--- a/spec/integration/qt.yml
+++ b/spec/integration/qt.yml
@@ -14,9 +14,22 @@ classes:
   "QMetaObject::Connection": SignalConnection
   SomeObject: SomeObject
   SomeGadget: SomeGadget
+  Conv: Conv
 
 types:
   "QMetaObject::Connection":
     crystal_type: SignalConnection
     cpp_type: "QMetaObject::Connection"
     binding_type: QMetaObjectConnection
+  Conv:
+    crystal_type: ConvCrystal
+    cpp_type: ConvCpp
+    binding_type: ConvBinding
+    to_cpp: "conv_to_cpp(%)"
+    from_cpp: "conv_from_cpp(%)"
+    to_crystal: "BindgenHelper.conv_to_crystal(%)"
+    from_crystal: "BindgenHelper.conv_from_crystal(%)"
+    kind: Struct
+    builtin: true
+    pass_by: Value
+    wrapper_pass_by: Value
diff --git a/spec/integration/qt_spec.cr b/spec/integration/qt_spec.cr
index 9e1ea7f..785bcff 100644
--- a/spec/integration/qt_spec.cr
+++ b/spec/integration/qt_spec.cr
@@ -3,6 +3,26 @@ require "./spec_helper"
 describe "Qt-specific wrapper features" do
   it "works" do
     build_and_run("qt") do
+      module Test
+        lib Binding
+          struct ConvBinding
+            x : Int32
+          end
+        end
+
+        alias ConvBinding = Binding::ConvBinding
+
+        module BindgenHelper
+          def conv_to_crystal(x : Binding::ConvBinding) : ConvCrystal
+            ConvCrystal.new
+          end
+
+          def conv_from_crystal(x : ConvCrystal) : Binding::ConvBinding
+            Binding::ConvBinding.new x: 0
+          end
+        end
+      end
+
       context "signal behaviour" do
         it "creates a on_X method" do
           subject = Test::SomeObject.new
diff --git a/src/bindgen/call_builder/cpp_qobject_connect.cr b/src/bindgen/call_builder/cpp_qobject_connect.cr
index 5d8b17b..a984e1f 100644
--- a/src/bindgen/call_builder/cpp_qobject_connect.cr
+++ b/src/bindgen/call_builder/cpp_qobject_connect.cr
@@ -18,16 +18,17 @@ module Bindgen
       end
 
       class Body < Call::Body
-        def initialize(@proc : Call)
+        def initialize(@lambda : Call)
         end
 
         def to_code(call : Call, platform : Graph::Platform) : String
           formatter = Cpp::Format.new
-          ptr = formatter.function_pointer(@proc)
-          lambda_args = formatter.argument_list(call.arguments)
 
-          inner = @proc.body.to_code(@proc, platform)
-          code = %[QObject::connect(_self_, (#{ptr})&#{call.name}, [_proc_](#{lambda_args}){ #{inner}; })]
+          lambda_body = @lambda.body.to_code(@lambda, platform)
+          ptr = formatter.function_pointer(@lambda)
+
+          code = %[QObject::connect(_self_, (#{ptr})&#{call.name}, #{lambda_body})]
+
           call.result.apply_conversion(code)
         end
       end
diff --git a/src/bindgen/call_builder/cpp_to_crystal_proc.cr b/src/bindgen/call_builder/cpp_to_crystal_proc.cr
index 41f3c23..0080f69 100644
--- a/src/bindgen/call_builder/cpp_to_crystal_proc.cr
+++ b/src/bindgen/call_builder/cpp_to_crystal_proc.cr
@@ -7,7 +7,9 @@ module Bindgen
       end
 
       # Calls the *method*, using the *proc_name* to call-through to Crystal.
-      def build(method : Parser::Method, proc_name : String = "_proc_") : Call
+      # If *lambda* is true, instead of invoking the *method*, builds a C++
+      # lambda expression that wraps the invocation.
+      def build(method : Parser::Method, *, proc_name : String = "_proc_", lambda = false) : Call
         pass = Cpp::Pass.new(@db)
 
         arguments = pass.arguments_from_cpp(method.arguments)
@@ -18,17 +20,34 @@ module Bindgen
           name: proc_name,
           result: result,
           arguments: arguments,
-          body: Body.new,
+          body: lambda ? LambdaBody.new : InvokeBody.new,
         )
       end
 
-      class Body < Call::Body
+      # Method invocation.
+      class InvokeBody < Call::Body
         def to_code(call : Call, platform : Graph::Platform) : String
           pass_args = call.arguments.map(&.call).join(", ")
           code = %[#{call.name}(#{pass_args})]
           call.result.apply_conversion(code)
         end
       end
+
+      # Lambda expression.  Captures the `CrystalProc` by value (therefore it
+      # is *not* convertible to a C function pointer).
+      class LambdaBody < Call::Body
+        def to_code(call : Call, platform : Graph::Platform) : String
+          formatter = Cpp::Format.new
+
+          lambda_args = formatter.argument_list(call.arguments)
+          pass_args = call.arguments.map(&.call).join(", ")
+          inner = %[#{call.name}(#{pass_args})]
+
+          prefix = "return " unless call.result.type.pure_void?
+
+          "[#{call.name}](#{lambda_args}){ #{prefix}#{inner}; }"
+        end
+      end
     end
   end
 end
diff --git a/src/bindgen/crystal/pass.cr b/src/bindgen/crystal/pass.cr
index 2bcbef2..af3681c 100644
--- a/src/bindgen/crystal/pass.cr
+++ b/src/bindgen/crystal/pass.cr
@@ -65,13 +65,18 @@ module Bindgen
             is_ref, ptr = reconfigure_pass_type(rules.pass_by, is_ref, ptr)
           end
 
+          if type.kind.function?
+            template = Template::ProcFromWrapper.new(type, @db).followed_by(template)
+          end
+
           ptr += 1 if is_ref # Translate reference to pointer
           is_ref = false
           {is_ref, ptr, type_name, template, false}
         end
       end
 
-      # Builds the type-name of a Crystal `Proc`, from the function *type*.
+      # Builds the type-name of a Crystal `Proc` for Crystal wrappers, from the
+      # function *type*.
       private def proc_to_wrapper(type)
         args = type.template.not_nil!.arguments
 
diff --git a/src/bindgen/processor/qt.cr b/src/bindgen/processor/qt.cr
index 8fb5107..9a4f337 100644
--- a/src/bindgen/processor/qt.cr
+++ b/src/bindgen/processor/qt.cr
@@ -90,7 +90,7 @@ module Bindgen
         call = CallBuilder::CppQobjectConnect.new(@db)
         wrapper = CallBuilder::CppWrapper.new(@db)
 
-        proc = to_proc.build(method)
+        proc = to_proc.build(method, lambda: true)
         connector.calls[Graph::Platform::Cpp] = wrapper.build(
           method: connector.origin,
           target: call.build(method, proc),
diff --git a/src/bindgen/processor/virtual_override.cr b/src/bindgen/processor/virtual_override.cr
index 850fa4a..adfe740 100644
--- a/src/bindgen/processor/virtual_override.cr
+++ b/src/bindgen/processor/virtual_override.cr
@@ -242,7 +242,7 @@ module Bindgen
           method: method,
           class_name: class_name,
           target: target,
-          virtual_target: to_crystal.build(method, proc_name),
+          virtual_target: to_crystal.build(method, proc_name: proc_name),
           in_superclass: in_superclass,
         )
       end