diff --git a/Python/ast.c b/Python/ast.c
index 1e182c7..ce61375 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -4282,7 +4282,7 @@
                     break;
                 start--;
             }
-            cols += substr - start;
+            cols += (int)(substr - start);
             /* Fix lineno in mulitline strings. */
             while ((substr = strchr(substr + 1, '\n')))
                 lines--;