diff --git a/extern/btyacc/reader.c b/extern/btyacc/reader.c
index 435e5ad3f48..8e2d9ed199d 100644
--- a/extern/btyacc/reader.c
+++ b/extern/btyacc/reader.c
@@ -146,11 +146,13 @@ char *get_line() {
 
   /* VM: Process %include line */
   if(strncmp(&line[0], "%include ", 9)==0) {
-    int ii=0;
-    for(i=9; line[i]!='\n' && line[i]!=' '; i++, ii++) {
-      inc_file_name[ii] = line[i];
-    }
-    inc_file_name[ii] = 0;
+
+    char *inc_file_name = line+9;
+    while (isspace(*inc_file_name)) inc_file_name++;
+    i = strlen(inc_file_name);
+    while (i > 0 && isspace(inc_file_name[i-1])) --i;
+    inc_file_name[i] = 0;
+
     if(inc_file) {
       error(lineno, 0, 0, "Nested include lines are not allowed");
     }