diff --git a/src/files.c b/src/files.c
--- a/src/files.c
+++ b/src/files.c
@@ -552,6 +552,12 @@
     return relocate_buffer;
   else
     {
+      char *bazel_runfiles_bison_pkgdatadir();
+      static char *bazel_pkgdatadir_p = NULL;
+      if (bazel_pkgdatadir_p == NULL) {
+        bazel_pkgdatadir_p = bazel_runfiles_bison_pkgdatadir();
+      }
+      if (bazel_pkgdatadir_p != NULL) { return bazel_pkgdatadir_p; }
       char const *cp = getenv ("BISON_PKGDATADIR");
       return cp ? cp : relocate2 (PKGDATADIR, &relocate_buffer);
     }
@@ -560,6 +566,12 @@
 char const *
 m4path (void)
 {
+  char *bazel_runfiles_m4();
+  static char *bazel_m4_p = NULL;
+  if (bazel_m4_p == NULL) {
+    bazel_m4_p = bazel_runfiles_m4();
+  }
+  if (bazel_m4_p != NULL) { return bazel_m4_p; }
   char const *m4 = getenv ("M4");
   if (m4)
     return m4;