diff --git a/crates/generate/src/generate.rs b/crates/generate/src/generate.rs
index 0cccefe8f..61d5e3f51 100644
--- a/crates/generate/src/generate.rs
+++ b/crates/generate/src/generate.rs
@@ -82,6 +82,8 @@ pub enum GenerateError {
     #[cfg(feature = "load")]
     #[error(transparent)]
     LoadGrammarFile(#[from] LoadGrammarError),
+    #[error("Grammar file `{0}` not found")]
+    GrammarFileNotFound(PathBuf),
     #[error(transparent)]
     ParseGrammar(#[from] ParseGrammarError),
     #[error(transparent)]
@@ -347,6 +349,11 @@ where
             .try_exists()
             .map_err(|e| GenerateError::GrammarPath(e.to_string()))?
         {
+            // A nonexistent path with an extension (i.e. tree-sitter-foo/grammar.json)
+            // is a missing input file, not a directory to create.
+            if path_buf.extension().is_some() {
+                return Err(GenerateError::GrammarFileNotFound(path_buf));
+            }
             fs::create_dir_all(&path_buf)
                 .map_err(|e| GenerateError::IO(IoError::new(e, Some(path_buf.as_path()))))?;
             repo_path = path_buf;