diff --git a/ui/build/rbe.go b/ui/build/rbe.go
index 6231e52..c3e52c6 100644
--- a/ui/build/rbe.go
+++ b/ui/build/rbe.go
@@ -94,6 +94,9 @@
 }
 
 func startRBE(ctx Context, config Config) {
+	if !config.GoogleProdCredsExist() && prodCredsAuthType(config) {
+		ctx.Fatalf("Unable to start RBE reproxy\nFAILED: Missing LOAS credentials.")
+	}
 	ctx.BeginTrace(metrics.RunSetupTool, "rbe_bootstrap")
 	defer ctx.EndTrace()