diff --git a/src/front/glsl/parser.rs b/src/front/glsl/parser.rs
index 1171b4d0a8..f16da82bac 100644
--- a/src/front/glsl/parser.rs
+++ b/src/front/glsl/parser.rs
@@ -244,10 +244,25 @@ pomelo! {
     function_call ::= function_call_or_method(fc) {
         match fc.kind {
             FunctionCallKind::TypeConstructor(ty) => {
-                let h = extra.context.expressions.append(Expression::Compose {
-                    ty,
-                    components: fc.args.iter().map(|a| a.expression).collect(),
-                });
+                let h = if fc.args.len() == 1 {
+                    let kind = match extra.module.types[ty].inner {
+                        TypeInner::Scalar{kind, ..} => kind,
+                        TypeInner::Vector{kind, ..} => kind,
+                        _ => {
+                            return Err(ErrorKind::SemanticError("Can only cast to scalar or vector"));
+                        }
+                    };
+                    extra.context.expressions.append(Expression::As {
+                        kind,
+                        expr: fc.args[0].expression,
+                        convert: true,
+                    })
+                } else {
+                    extra.context.expressions.append(Expression::Compose {
+                        ty,
+                        components: fc.args.iter().map(|a| a.expression).collect(),
+                    })
+                };
                 ExpressionRule {
                     expression: h,
                     statements: fc.args.into_iter().map(|a| a.statements).flatten().collect(),