diff --git a/sphinx/domains/c.py b/sphinx/domains/c.py
index ff592d0de..125bf067b 100644
--- a/sphinx/domains/c.py
+++ b/sphinx/domains/c.py
@@ -111,7 +111,7 @@ _simple_type_sepcifiers_re = re.compile(r"""(?x)
     |__float80|_Float64x|__float128|_Float128|__ibm128
     |__fp16
     # Fixed-point, extension
-    |(_Sat\s+)?((signed|unsigned)\s+)?((short|long|long\s+long)\s+)?(_Fract|_Accum)
+    |(_Sat\s+)?((signed|unsigned)\s+)?((short|long|long\s+long)\s+)?(_Fract|fract|_Accum|accum)
     # Integer types that could be prefixes of the previous ones
     # ---------------------------------------------------------
     |((signed|unsigned)\s+)?(short|long\s+long|long)
diff --git a/tests/test_domain_c.py b/tests/test_domain_c.py
index d8429861a..b910a2ec8 100644
--- a/tests/test_domain_c.py
+++ b/tests/test_domain_c.py
@@ -318,7 +318,7 @@ def test_domain_c_ast_fundamental_types():
         # -----------------------------
         # https://gcc.gnu.org/onlinedocs/gcc/Fixed-Point.html#Fixed-Point
         for sat in ('', '_Sat '):
-            for t in ('_Fract', '_Accum'):
+            for t in ('_Fract', 'fract', '_Accum', 'accum'):
                 for size in ('short ', '', 'long ', 'long long '):
                     for tt in signed(size + t):
                         yield sat + tt