diff --git a/src/vs/workbench/services/search/node/fileSearch.ts b/src/vs/workbench/services/search/node/fileSearch.ts
index 9e111e328ae40bbbcdf9064eb42d3eaf7bdd8c55..d4dbfca86c350707a21e2e93e7bae7781aa599d3 100644
--- a/src/vs/workbench/services/search/node/fileSearch.ts
+++ b/src/vs/workbench/services/search/node/fileSearch.ts
@@ -44,7 +44,7 @@ export class FileWalker {
 		this.walkedPaths = Object.create(null);
 
 		// Normalize file patterns to forward slashs
-		if (this.filePattern.indexOf(paths.sep) >= 0) {
+		if (this.filePattern && this.filePattern.indexOf(paths.sep) >= 0) {
 			this.filePattern = strings.replaceAll(this.filePattern, '\\', '/');
 			this.searchInPath = true;
 		}
@@ -240,4 +240,4 @@ export class Engine implements ISearchEngine {
 	public cancel(): void {
 		this.walker.cancel();
 	}
-}
\ No newline at end of file
+}