diff --git a/src/docbuilder/rustwide_builder.rs b/src/docbuilder/rustwide_builder.rs
index eb5010bd7..38db2ec0b 100644
--- a/src/docbuilder/rustwide_builder.rs
+++ b/src/docbuilder/rustwide_builder.rs
@@ -219,6 +219,7 @@ impl RustwideBuilder {
     }
 
     pub fn add_essential_files(&mut self) -> Result<()> {
+        self.rustc_version = self.detect_rustc_version()?;
         let rustc_version = parse_rustc_version(&self.rustc_version)?;
 
         info!("building a dummy crate to get essential files");