diff --git a/dtool/src/cppparser/cppPreprocessor.cxx b/dtool/src/cppparser/cppPreprocessor.cxx
index 26ba349019..6b4c8addab 100644
--- a/dtool/src/cppparser/cppPreprocessor.cxx
+++ b/dtool/src/cppparser/cppPreprocessor.cxx
@@ -602,6 +602,7 @@ push_file(const CPPFile &file) {
 
     infile._prev_last_c = _last_c;
     _last_c = '\0';
+    _start_of_line = true;
     return true;
   }