diff --git a/archivers/grp.c b/archivers/grp.c
index 6959735..e05d76b 100644
--- a/archivers/grp.c
+++ b/archivers/grp.c
@@ -76,6 +76,7 @@ static LinkedStringList *GRP_enumerateFiles(DirHandle *h,
 static int GRP_exists(DirHandle *h, const char *name);
 static int GRP_isDirectory(DirHandle *h, const char *name);
 static int GRP_isSymLink(DirHandle *h, const char *name);
+static PHYSFS_sint64 GRP_getLastModTime(DirHandle *h, const char *name);
 static FileHandle *GRP_openRead(DirHandle *h, const char *name);
 
 static const FileFunctions __PHYSFS_FileFunctions_GRP =
@@ -98,7 +99,7 @@ const DirFunctions __PHYSFS_DirFunctions_GRP =
     GRP_exists,             /* exists() method         */
     GRP_isDirectory,        /* isDirectory() method    */
     GRP_isSymLink,          /* isSymLink() method      */
-    NULL,                   /* getLastModTime() method */
+    GRP_getLastModTime,     /* getLastModTime() method */
     GRP_openRead,           /* openRead() method       */
     NULL,                   /* openWrite() method      */
     NULL,                   /* openAppend() method     */
@@ -404,6 +405,13 @@ static int GRP_isSymLink(DirHandle *h, const char *name)
 } /* GRP_isSymLink */
 
 
+static PHYSFS_sint64 GRP_getLastModTime(DirHandle *h, const char *name)
+{
+    /* Just return the time of the GRP itself in the physical filesystem. */
+    return(__PHYSFS_platformGetLastModTime(((GRPinfo *) h->opaque)->filename));
+} /* GRP_getLastModTime */
+
+
 static FileHandle *GRP_openRead(DirHandle *h, const char *name)
 {
     const char *filename = ((GRPinfo *) h->opaque)->filename;