--- a/editor/png2inc.c
+++ b/editor/png2inc.c
@@ -556,11 +556,11 @@
     if ((strstr(filename, LADDERS_SUFFIX) == NULL) && (strstr(filename, ENTITIES_SUFFIX) == NULL)) {
       char ladders_file[256] = {0};
       strncpy(ladders_file, filename, filename_len - 4);
-      strncpy(ladders_file + strlen(ladders_file), LADDERS_SUFFIX, sizeof(ladders_file) - strlen(LADDERS_SUFFIX) - 4);
+      strncpy(ladders_file + strlen(ladders_file), LADDERS_SUFFIX, sizeof(ladders_file) - strlen(ladders_file) - 1);
 
       char entities_file[256] = {0};
       strncpy(entities_file, filename, filename_len - 4);
-      strncpy(entities_file + strlen(entities_file), ENTITIES_SUFFIX, sizeof(entities_file) - strlen(ENTITIES_SUFFIX) - 4);
+      strncpy(entities_file + strlen(entities_file), ENTITIES_SUFFIX, sizeof(entities_file) - strlen(entities_file) - 1);
 
       uint32_t map_width;
       uint32_t map_height;