diff --git a/lib/gis/locale.c b/lib/gis/locale.c
index f1aabf31f71..16b9acd289c 100644
--- a/lib/gis/locale.c
+++ b/lib/gis/locale.c
@@ -39,7 +39,9 @@ void G_init_locale(void)
 #ifdef LC_MESSAGES
     setlocale(LC_MESSAGES, "");
 #endif
-    const char *localedir = G_locale_dir();
+    /* Not using G_locale_dir(): its G_fatal_error() would translate the
+       message and re-enter G_init_locale(), recursing without bound. */
+    const char *localedir = getenv("GRASS_LOCALEDIR");
 
     if (localedir && *localedir) {
         bindtextdomain("grasslibs", localedir);
diff --git a/lib/gis/resource_dirs.c b/lib/gis/resource_dirs.c
index 8602ceefe49..8560cb4b671 100644
--- a/lib/gis/resource_dirs.c
+++ b/lib/gis/resource_dirs.c
@@ -10,44 +10,61 @@
    SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+#include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include <grass/gis.h>
 #include <grass/glocale.h>
 
-static const char *get_g_env(const char *);
+static const char *get_g_env(const char *, const char *);
 
 const char *G_colors_dir(void)
 {
-    return get_g_env("GRASS_COLORSDIR");
+    return get_g_env("GRASS_COLORSDIR", "etc/colors");
 }
 
 const char *G_etcbin_dir(void)
 {
-    return get_g_env("GRASS_ETCBINDIR");
+    return get_g_env("GRASS_ETCBINDIR", "etc");
 }
 
 const char *G_etc_dir(void)
 {
-    return get_g_env("GRASS_ETCDIR");
+    return get_g_env("GRASS_ETCDIR", "etc");
 }
 
 const char *G_fonts_dir(void)
 {
-    return get_g_env("GRASS_FONTSDIR");
+    return get_g_env("GRASS_FONTSDIR", "fonts");
 }
 
 const char *G_locale_dir(void)
 {
-    return get_g_env("GRASS_LOCALEDIR");
+    return get_g_env("GRASS_LOCALEDIR", "locale");
 }
 
-static const char *get_g_env(const char *env_var)
+/*!
+   \brief Get a resource directory from the environment.
+
+   Falls back to the legacy (non-FHS) location relative to GISBASE when
+   the variable is not set. Fatal when neither yields an existing path.
+ */
+static const char *get_g_env(const char *env_var, const char *gisbase_rel_dir)
 {
     const char *value = getenv(env_var);
     if (value)
         return value;
 
+    const char *gisbase = getenv("GISBASE");
+    if (gisbase && *gisbase) {
+        char path[GPATH_MAX];
+
+        snprintf(path, sizeof(path), "%s/%s", gisbase, gisbase_rel_dir);
+        if (access(path, F_OK) == 0)
+            return G_store(path);
+    }
+
     G_fatal_error(_("Incomplete GRASS session: Variable '%s' not set"),
                   env_var);
 }