diff --git a/lib/IDE/CompletionInstance.cpp b/lib/IDE/CompletionInstance.cpp
index 632a3b5f6542a..44dbf98a3fadd 100644
--- a/lib/IDE/CompletionInstance.cpp
+++ b/lib/IDE/CompletionInstance.cpp
@@ -324,6 +324,11 @@ bool swift::ide::CompletionInstance::performOperation(
   // source text. That breaks an invariant of syntax tree building.
   Invocation.getLangOptions().BuildSyntaxTree = false;
 
+  // This validation may call stat(2) many times. Disable it to prevent
+  // performance regression.
+  Invocation.getSearchPathOptions().DisableModulesValidateSystemDependencies =
+      true;
+
   // FIXME: ASTScopeLookup doesn't support code completion yet.
   Invocation.disableASTScopeLookup();