diff --git a/src/core/BeforeCall.go b/src/core/BeforeCall.go
deleted file mode 100644
index 57812f8..0000000
--- a/src/core/BeforeCall.go
+++ /dev/null
@@ -1,32 +0,0 @@
-package core
-
-import (
-	"git.akyoto.dev/cli/q/src/cpu"
-	"git.akyoto.dev/cli/q/src/errors"
-	"git.akyoto.dev/cli/q/src/expression"
-	"git.akyoto.dev/cli/q/src/token"
-	"git.akyoto.dev/cli/q/src/types"
-)
-
-// BeforeCall loads the registers with the parameter values and checks that the types match with the function signature.
-func (f *Function) BeforeCall(fn *Function, parameters []*expression.Expression, registers []cpu.Register) error {
-	for i := len(parameters) - 1; i >= 0; i-- {
-		typ, err := f.ExpressionToRegister(parameters[i], registers[i])
-
-		if err != nil {
-			return err
-		}
-
-		if !types.Is(typ, fn.Input[i].Type) {
-			_, expectsPointer := fn.Input[i].Type.(*types.Pointer)
-
-			if expectsPointer && parameters[i].Token.Kind == token.Number && parameters[i].Token.Text(f.File.Bytes) == "0" {
-				continue
-			}
-
-			return errors.New(&errors.TypeMismatch{Encountered: typ.Name(), Expected: fn.Input[i].Type.Name(), ParameterName: fn.Input[i].Name}, f.File, parameters[i].Token.Position)
-		}
-	}
-
-	return nil
-}
diff --git a/src/core/CallExtern.go b/src/core/CallExtern.go
index abb1a7a..1b8fe8f 100644
--- a/src/core/CallExtern.go
+++ b/src/core/CallExtern.go
@@ -26,7 +26,7 @@ func (f *Function) CallExtern(fn *Function, parameters []*expression.Expression)
 	}
 
 	registers := x86.WindowsInputRegisters[:len(parameters)]
-	err := f.BeforeCall(fn, parameters, registers)
+	err := f.ExpressionsToRegisters(parameters, registers, fn.Input)
 
 	if err != nil {
 		return nil, err
diff --git a/src/core/CompileCall.go b/src/core/CompileCall.go
index 2518ab5..86f284b 100644
--- a/src/core/CompileCall.go
+++ b/src/core/CompileCall.go
@@ -75,7 +75,7 @@ func (f *Function) CompileCall(root *expression.Expression) ([]types.Type, error
 	}
 
 	registers := f.CPU.Input[:len(parameters)]
-	err := f.BeforeCall(fn, parameters, registers)
+	err := f.ExpressionsToRegisters(parameters, registers, fn.Input)
 
 	if err != nil {
 		return nil, err
diff --git a/src/core/CompileReturn.go b/src/core/CompileReturn.go
index 87050e8..752669f 100644
--- a/src/core/CompileReturn.go
+++ b/src/core/CompileReturn.go
@@ -18,6 +18,7 @@ func (f *Function) CompileReturn(node *ast.Return) error {
 	}
 
 	for i := len(node.Values) - 1; i >= 0; i-- {
+		f.SaveRegister(f.CPU.Output[i])
 		typ, err := f.ExpressionToRegister(node.Values[i], f.CPU.Output[i])
 
 		if err != nil {
diff --git a/src/core/CompileSyscall.go b/src/core/CompileSyscall.go
index cadce36..0b3b1d6 100644
--- a/src/core/CompileSyscall.go
+++ b/src/core/CompileSyscall.go
@@ -8,7 +8,7 @@ import (
 func (f *Function) CompileSyscall(root *expression.Expression) error {
 	parameters := root.Children[1:]
 	registers := f.CPU.SyscallInput[:len(parameters)]
-	err := f.ExpressionsToRegisters(parameters, registers)
+	err := f.ExpressionsToRegisters(parameters, registers, nil)
 
 	if err != nil {
 		return err
diff --git a/src/core/ExpressionToRegister.go b/src/core/ExpressionToRegister.go
index 4dfb2d7..d690f7f 100644
--- a/src/core/ExpressionToRegister.go
+++ b/src/core/ExpressionToRegister.go
@@ -12,8 +12,6 @@ import (
 
 // ExpressionToRegister puts the result of an expression into the specified register.
 func (f *Function) ExpressionToRegister(node *expression.Expression, register cpu.Register) (types.Type, error) {
-	f.SaveRegister(register)
-
 	if node.IsFolded {
 		f.RegisterNumber(asm.MOVE, register, node.Value)
 		return types.Int, nil
diff --git a/src/core/ExpressionsToRegisters.go b/src/core/ExpressionsToRegisters.go
index 4f2dbed..8d1436a 100644
--- a/src/core/ExpressionsToRegisters.go
+++ b/src/core/ExpressionsToRegisters.go
@@ -2,17 +2,35 @@ package core
 
 import (
 	"git.akyoto.dev/cli/q/src/cpu"
+	"git.akyoto.dev/cli/q/src/errors"
 	"git.akyoto.dev/cli/q/src/expression"
+	"git.akyoto.dev/cli/q/src/token"
+	"git.akyoto.dev/cli/q/src/types"
 )
 
-// ExpressionsToRegisters moves multiple expressions into the specified registers.
-func (f *Function) ExpressionsToRegisters(expressions []*expression.Expression, registers []cpu.Register) error {
+// ExpressionsToRegisters moves multiple expressions into the specified registers and checks that the types match with the function signature.
+func (f *Function) ExpressionsToRegisters(expressions []*expression.Expression, registers []cpu.Register, input []*Input) error {
 	for i := len(expressions) - 1; i >= 0; i-- {
-		_, err := f.ExpressionToRegister(expressions[i], registers[i])
+		f.SaveRegister(registers[i])
+		typ, err := f.ExpressionToRegister(expressions[i], registers[i])
 
 		if err != nil {
 			return err
 		}
+
+		if input == nil {
+			continue
+		}
+
+		if !types.Is(typ, input[i].Type) {
+			_, expectsPointer := input[i].Type.(*types.Pointer)
+
+			if expectsPointer && expressions[i].Token.Kind == token.Number && expressions[i].Token.Text(f.File.Bytes) == "0" {
+				continue
+			}
+
+			return errors.New(&errors.TypeMismatch{Encountered: typ.Name(), Expected: input[i].Type.Name(), ParameterName: input[i].Name}, f.File, expressions[i].Token.Position)
+		}
 	}
 
 	return nil