diff --git a/src/bootstrap/src/bin/rustc.rs b/src/bootstrap/src/bin/rustc.rs
index 38c55b2034496..a9dd687b75653 100644
--- a/src/bootstrap/src/bin/rustc.rs
+++ b/src/bootstrap/src/bin/rustc.rs
@@ -161,13 +161,17 @@ fn main() {
     }
 
     if let Ok(map) = env::var("RUSTC_DEBUGINFO_MAP") {
-        cmd.arg("--remap-path-prefix").arg(&map);
+        if !map.is_empty() {
+            cmd.arg("--remap-path-prefix").arg(&map);
+        }
     }
     // The remap flags for Cargo registry sources need to be passed after the remapping for the
     // Rust source code directory, to handle cases when $CARGO_HOME is inside the source directory.
     if let Ok(maps) = env::var("RUSTC_CARGO_REGISTRY_SRC_TO_REMAP") {
         for map in maps.split('\t') {
-            cmd.arg("--remap-path-prefix").arg(map);
+            if !map.is_empty() {
+                cmd.arg("--remap-path-prefix").arg(map);
+            }
         }
     }
 
diff --git a/src/bootstrap/src/core/builder.rs b/src/bootstrap/src/core/builder.rs
index e85753a351232..08e7e0b348096 100644
--- a/src/bootstrap/src/core/builder.rs
+++ b/src/bootstrap/src/core/builder.rs
@@ -1812,15 +1812,19 @@ impl<'a> Builder<'a> {
         if self.config.rust_remap_debuginfo {
             // FIXME: handle vendored sources
             let registry_src = t!(home::cargo_home()).join("registry").join("src");
-            let mut env_var = OsString::new();
-            for entry in t!(std::fs::read_dir(registry_src)) {
+            if registry_src.is_dir() {
+                let mut env_var = OsString::new();
+                for entry in t!(std::fs::read_dir(registry_src)) {
+                    if !env_var.is_empty() {
+                        env_var.push("\t");
+                    }
+                    env_var.push(t!(entry).path());
+                    env_var.push("=/rust/deps");
+                }
                 if !env_var.is_empty() {
-                    env_var.push("\t");
+                    cargo.env("RUSTC_CARGO_REGISTRY_SRC_TO_REMAP", env_var);
                 }
-                env_var.push(t!(entry).path());
-                env_var.push("=/rust/deps");
             }
-            cargo.env("RUSTC_CARGO_REGISTRY_SRC_TO_REMAP", env_var);
         }
 
         // Enable usage of unstable features