diff --git a/cli/file_fetcher.rs b/cli/file_fetcher.rs
index 5b2f6f74cb..a17a8fc247 100644
--- a/cli/file_fetcher.rs
+++ b/cli/file_fetcher.rs
@@ -26,7 +26,7 @@ use std::pin::Pin;
 use std::sync::Arc;
 use std::sync::Mutex;
 
-const SUPPORTED_SCHEMES: [&str; 3] = ["http", "https", "file"];
+pub const SUPPORTED_SCHEMES: [&str; 3] = ["http", "https", "file"];
 
 /// A structure representing a source file.
 #[derive(Debug, Clone, Eq, PartialEq)]
diff --git a/cli/lsp/sources.rs b/cli/lsp/sources.rs
index c6a15461ff..09b0a4cc8b 100644
--- a/cli/lsp/sources.rs
+++ b/cli/lsp/sources.rs
@@ -5,6 +5,7 @@ use super::text;
 
 use crate::file_fetcher::get_source_from_bytes;
 use crate::file_fetcher::map_content_type;
+use crate::file_fetcher::SUPPORTED_SCHEMES;
 use crate::http_cache;
 use crate::http_cache::HttpCache;
 use crate::import_map::ImportMap;
@@ -279,7 +280,12 @@ impl Sources {
     &mut self,
     specifier: &ModuleSpecifier,
   ) -> Option<ModuleSpecifier> {
-    if specifier.as_url().scheme() == "file" {
+    let scheme = specifier.as_url().scheme();
+    if !SUPPORTED_SCHEMES.contains(&scheme) {
+      return None;
+    }
+
+    if scheme == "file" {
       if let Ok(path) = specifier.as_url().to_file_path() {
         if path.is_file() {
           return Some(specifier.clone());
@@ -377,4 +383,13 @@ mod tests {
     let actual = actual.unwrap();
     assert_eq!(actual, 28);
   }
+
+  #[test]
+  fn test_sources_resolve_specifier_non_supported_schema() {
+    let (mut sources, _) = setup();
+    let specifier = ModuleSpecifier::resolve_url("foo://a/b/c.ts")
+      .expect("could not create specifier");
+    let actual = sources.resolve_specifier(&specifier);
+    assert!(actual.is_none());
+  }
 }