diff --git a/src/server/project.ts b/src/server/project.ts
index 10782ed4bb8..e0b938a3892 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -690,7 +690,7 @@ namespace ts.server {
         }
 
         getEffectiveTypeRoots() {
-            return ts.getEffectiveTypeRoots(this.getCompilerOptions(), this.projectService.host);
+            return ts.getEffectiveTypeRoots(this.getCompilerOptions(), this.projectService.host) || [];
         }
     }