diff --git a/gcc/c-family/c-format.cc b/gcc/c-family/c-format.cc
index 4559ca3..7547804 100644
--- a/gcc/c-family/c-format.cc
+++ b/gcc/c-family/c-format.cc
@@ -1742,7 +1742,8 @@
     }
   tree underlying_type
     = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (format_tree)));
-  if (underlying_type != char_type_node)
+  if (underlying_type != char_type_node
+      && !(flag_char8_t && underlying_type == char8_type_node))
     {
       if (underlying_type == char16_type_node
 	  || underlying_type == char32_type_node
diff --git a/gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C b/gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C
new file mode 100644
index 0000000..ba6f388
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wformat-char8_t-1.C
@@ -0,0 +1,10 @@
+// PR c++/105626
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wformat" }
+// { dg-additional-options "-fchar8_t" { target c++17_down } }
+
+int main()
+{
+  __builtin_printf((const char*) u8"test %d\n", 1); // { dg-bogus "format string" }
+  return 0;
+}