diff --git a/src/builder.rs b/src/builder.rs
index 2c5ae3fff7b..0939c84144e 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -520,8 +520,7 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
         self.block
     }
 
-    fn append_block(cx: &'a CodegenCx<'gcc, 'tcx>, func: RValue<'gcc>, name: &str) -> Block<'gcc> {
-        let func = cx.rvalue_as_function(func);
+    fn append_block(_: &'a CodegenCx<'gcc, 'tcx>, func: Function<'gcc>, name: &str) -> Block<'gcc> {
         func.new_block(name)
     }
 
diff --git a/src/context.rs b/src/context.rs
index 8a2bf654ed2..45b3bd06e13 100644
--- a/src/context.rs
+++ b/src/context.rs
@@ -375,8 +375,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
 impl<'gcc, 'tcx> BackendTypes for CodegenCx<'gcc, 'tcx> {
     type Value = RValue<'gcc>;
     type Metadata = RValue<'gcc>;
-    // TODO(antoyo): change to Function<'gcc>.
-    type Function = RValue<'gcc>;
+    type Function = Function<'gcc>;
 
     type BasicBlock = Block<'gcc>;
     type Type = Type<'gcc>;
@@ -394,11 +393,10 @@ impl<'gcc, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         &self.vtables
     }
 
-    fn get_fn(&self, instance: Instance<'tcx>) -> RValue<'gcc> {
+    fn get_fn(&self, instance: Instance<'tcx>) -> Function<'gcc> {
         let func = get_fn(self, instance);
         *self.current_func.borrow_mut() = Some(func);
-        // FIXME(antoyo): this is a wrong cast. That requires changing the compiler API.
-        unsafe { std::mem::transmute(func) }
+        func
     }
 
     fn get_fn_addr(&self, instance: Instance<'tcx>) -> RValue<'gcc> {
@@ -487,11 +485,11 @@ impl<'gcc, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         self.codegen_unit
     }
 
-    fn set_frame_pointer_type(&self, _llfn: RValue<'gcc>) {
+    fn set_frame_pointer_type(&self, _llfn: Function<'gcc>) {
         // TODO(antoyo)
     }
 
-    fn apply_target_cpu_attr(&self, _llfn: RValue<'gcc>) {
+    fn apply_target_cpu_attr(&self, _llfn: Function<'gcc>) {
         // TODO(antoyo)
     }
 
diff --git a/src/debuginfo.rs b/src/debuginfo.rs
index e0597d0030d..66ef12d2a85 100644
--- a/src/debuginfo.rs
+++ b/src/debuginfo.rs
@@ -1,7 +1,7 @@
 use std::ops::Range;
 use std::sync::Arc;
 
-use gccjit::{Location, RValue};
+use gccjit::{Function, Location, RValue};
 use rustc_abi::Size;
 use rustc_codegen_ssa::mir::debuginfo::{DebugScope, FunctionDebugContext, VariableKind};
 use rustc_codegen_ssa::traits::{DebugInfoBuilderMethods, DebugInfoCodegenMethods};
@@ -225,7 +225,7 @@ impl<'gcc, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         &self,
         instance: Instance<'tcx>,
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
-        llfn: RValue<'gcc>,
+        llfn: Function<'gcc>,
         mir: &mir::Body<'tcx>,
     ) -> Option<FunctionDebugContext<'tcx, Self::DIScope, Self::DILocation>> {
         if self.sess().opts.debuginfo == DebugInfo::None {
@@ -276,7 +276,7 @@ impl<'gcc, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         &self,
         _instance: Instance<'tcx>,
         _fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
-        _maybe_definition_llfn: Option<RValue<'gcc>>,
+        _maybe_definition_llfn: Option<Function<'gcc>>,
     ) -> Self::DIScope {
         // TODO(antoyo): implement.
     }
diff --git a/src/declare.rs b/src/declare.rs
index bed82073e2c..691fd8729e3 100644
--- a/src/declare.rs
+++ b/src/declare.rs
@@ -94,7 +94,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
         _fn_type: Type<'gcc>,
         #[cfg(feature = "master")] callconv: Option<FnAttribute<'gcc>>,
         #[cfg(not(feature = "master"))] callconv: Option<()>,
-    ) -> RValue<'gcc> {
+    ) -> Function<'gcc> {
         // TODO(antoyo): use the fn_type parameter.
         let const_string = self.context.new_type::<u8>().make_pointer().make_pointer();
         let return_type = self.type_i32();
@@ -111,8 +111,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
         // NOTE: it is needed to set the current_func here as well, because get_fn() is not called
         // for the main function.
         *self.current_func.borrow_mut() = Some(func);
-        // FIXME(antoyo): this is a wrong cast. That requires changing the compiler API.
-        unsafe { std::mem::transmute(func) }
+        func
     }
 
     pub fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> Function<'gcc> {
diff --git a/src/intrinsic/mod.rs b/src/intrinsic/mod.rs
index ba85bc2beff..8401e78bd2f 100644
--- a/src/intrinsic/mod.rs
+++ b/src/intrinsic/mod.rs
@@ -1484,10 +1484,9 @@ fn gen_fn<'a, 'gcc, 'tcx>(
     // FIXME(eddyb) find a nicer way to do this.
     cx.linkage.set(FunctionType::Internal);
     let func = cx.declare_fn(name, fn_abi);
-    let func_val = unsafe { std::mem::transmute::<Function<'gcc>, RValue<'gcc>>(func) };
-    cx.set_frame_pointer_type(func_val);
-    cx.apply_target_cpu_attr(func_val);
-    let block = Builder::append_block(cx, func_val, "entry-block");
+    cx.set_frame_pointer_type(func);
+    cx.apply_target_cpu_attr(func);
+    let block = Builder::append_block(cx, func, "entry-block");
     let bx = Builder::build(cx, block);
     codegen(bx);
     (return_type, func)