diff --git a/naga/src/front/wgsl/error.rs b/naga/src/front/wgsl/error.rs
index 08c6dc2c5f..eeab34d47c 100644
--- a/naga/src/front/wgsl/error.rs
+++ b/naga/src/front/wgsl/error.rs
@@ -283,6 +283,10 @@ pub(crate) enum Error<'a> {
         kind: UnimplementedEnableExtension,
         span: Span,
     },
+    EnableExtensionNotEnabled {
+        kind: EnableExtension,
+        span: Span,
+    },
 }
 
 #[derive(Clone, Debug)]
@@ -945,6 +949,33 @@ impl<'a> Error<'a> {
                     kind.tracking_issue_num()
                 )],
             },
+            Error::EnableExtensionNotEnabled { kind, span } => ParseError {
+                message: format!("`{}` enable extension is not enabled", kind.to_ident()),
+                labels: vec![(
+                    span,
+                    format!(
+                        concat!(
+                            "the `{}` enable extension is needed for this functionality, ",
+                            "but it is not currently enabled"
+                        ),
+                        kind.to_ident()
+                    )
+                    .into(),
+                )],
+                notes: if let EnableExtension::Unimplemented(kind) = kind {
+                    vec![format!(
+                        concat!(
+                            "This extension is not yet implemented. ",
+                            "Let Naga maintainers know that you ran into this at ",
+                            "<https://github.com/gfx-rs/wgpu/issues/{}>, ",
+                            "so they can prioritize it!"
+                        ),
+                        kind.tracking_issue_num()
+                    )]
+                } else {
+                    vec![]
+                },
+            },
         }
     }
 }
diff --git a/naga/src/front/wgsl/parse/mod.rs b/naga/src/front/wgsl/parse/mod.rs
index b1262dcc3a..ca35015943 100644
--- a/naga/src/front/wgsl/parse/mod.rs
+++ b/naga/src/front/wgsl/parse/mod.rs
@@ -1,5 +1,7 @@
 use crate::front::wgsl::error::{Error, ExpectedToken};
-use crate::front::wgsl::parse::directive::enable_extension::{EnableExtension, EnableExtensions};
+use crate::front::wgsl::parse::directive::enable_extension::{
+    EnableExtension, EnableExtensions, UnimplementedEnableExtension,
+};
 use crate::front::wgsl::parse::directive::DirectiveKind;
 use crate::front::wgsl::parse::lexer::{Lexer, Token};
 use crate::front::wgsl::parse::number::Number;
@@ -667,7 +669,15 @@ impl Parser {
             }
             (Token::Number(res), span) => {
                 let _ = lexer.next();
-                let num = res.map_err(|err| Error::BadNumber(span, err))?;
+                let num = res.map_err(|err| match err {
+                    super::error::NumberError::UnimplementedF16 => {
+                        Error::EnableExtensionNotEnabled {
+                            kind: EnableExtension::Unimplemented(UnimplementedEnableExtension::F16),
+                            span,
+                        }
+                    }
+                    err => Error::BadNumber(span, err),
+                })?;
                 ast::Expression::Literal(ast::Literal::Number(num))
             }
             (Token::Word("RAY_FLAG_NONE"), _) => {