diff --git a/include/cantera/base/smart_ptr.h b/include/cantera/base/smart_ptr.h
index 685cadb50..b4a4299ee 100644
--- a/include/cantera/base/smart_ptr.h
+++ b/include/cantera/base/smart_ptr.h
@@ -1,3 +1,6 @@
+#ifndef CT_SMART_PTR
+#define CT_SMART_PTR
+
 #include "config.h"
 
 #if defined CT_USE_STD_SHARED_PTR
@@ -31,3 +34,5 @@ namespace Cantera
 #else
 #error "No shared_ptr implementation available"
 #endif
+
+#endif