diff --git a/gallery_dl/extractor/idolcomplex.py b/gallery_dl/extractor/idolcomplex.py
index 6da2aca6..a8f1298f 100644
--- a/gallery_dl/extractor/idolcomplex.py
+++ b/gallery_dl/extractor/idolcomplex.py
@@ -11,7 +11,8 @@
 from . import sankaku
 
 BASE_PATTERN = (r"(?:https?://)?(?:www\.)?"
-                r"idol(?:\.sankaku)?complex\.com(?:/[a-z]{2})?")
+                r"idol(?:\.sankaku)?complex\.com"
+                r"(?:/[a-z]{2}(?:[-_][A-Z]{2})?)?")
 
 
 class IdolcomplexBase():
diff --git a/gallery_dl/extractor/sankaku.py b/gallery_dl/extractor/sankaku.py
index 9fcde364..848ae96a 100644
--- a/gallery_dl/extractor/sankaku.py
+++ b/gallery_dl/extractor/sankaku.py
@@ -16,7 +16,7 @@ import collections
 
 BASE_PATTERN = r"(?:https?://)?" \
     r"(?:(?:chan|www|beta|black|white)\.sankakucomplex\.com|sankaku\.app)" \
-    r"(?:/[a-z]{2})?"
+    r"(?:/[a-z]{2}(?:[-_][A-Z]{2})?)?"
 
 
 class SankakuExtractor(BooruExtractor):
diff --git a/test/results/idolcomplex.py b/test/results/idolcomplex.py
index 703d4c4e..93b103df 100644
--- a/test/results/idolcomplex.py
+++ b/test/results/idolcomplex.py
@@ -18,6 +18,13 @@ __tests__ = (
     "#count"   : 5,
 },
 
+{
+    "#url"     : "https://www.idolcomplex.com/zh-CN/posts?tags=lyumos",
+    "#comment" : "locale code (ISO 639-1 + ISO 3166-1) (#8667)",
+    "#category": ("booru", "idolcomplex", "tag"),
+    "#class"   : idolcomplex.IdolcomplexTagExtractor,
+},
+
 {
     "#url"     : "https://idolcomplex.com/posts?tags=lyumos",
     "#category": ("booru", "idolcomplex", "tag"),
diff --git a/test/results/sankaku.py b/test/results/sankaku.py
index ce76af64..8368c9af 100644
--- a/test/results/sankaku.py
+++ b/test/results/sankaku.py
@@ -49,12 +49,28 @@ __tests__ = (
 
 {
     "#url"     : "https://sankaku.app/ja?tags=order%3Apopularity",
+    "#comment" : "ISO 639-1",
     "#category": ("booru", "sankaku", "tag"),
     "#class"   : sankaku.SankakuTagExtractor,
 },
 
 {
     "#url"     : "https://sankaku.app/no/?tags=order%3Apopularity",
+    "#comment" : "ISO 639-1 with trailing '/'",
+    "#category": ("booru", "sankaku", "tag"),
+    "#class"   : sankaku.SankakuTagExtractor,
+},
+
+{
+    "#url"     : "https://sankaku.app/zh-CN/?tags=order%3Apopularity",
+    "#comment" : "locale code (ISO 639-1 + ISO 3166-1) (#8667)",
+    "#category": ("booru", "sankaku", "tag"),
+    "#class"   : sankaku.SankakuTagExtractor,
+},
+
+{
+    "#url"     : "https://sankaku.app/zh_CN/?tags=order%3Apopularity",
+    "#comment" : "locale code (ISO 639-1 + ISO 3166-1) (#8667)",
     "#category": ("booru", "sankaku", "tag"),
     "#class"   : sankaku.SankakuTagExtractor,
 },