Index: runtime/src/kmp_gsupport.c
===================================================================
--- runtime/src/kmp_gsupport.c
+++ runtime/src/kmp_gsupport.c
@@ -1259,7 +1259,7 @@
 void
 xexpand(KMP_API_NAME_GOMP_TASKGROUP_START)(void)
 {
-    int gtid = __kmp_get_gtid();
+    int gtid = __kmp_entry_gtid();
     MKLOC(loc, "GOMP_taskgroup_start");
     KA_TRACE(20, ("GOMP_taskgroup_start: T#%d\n", gtid));
 
Index: runtime/test/tasking/bug_serial_taskgroup.c
===================================================================
--- /dev/null
+++ runtime/test/tasking/bug_serial_taskgroup.c
@@ -0,0 +1,16 @@
+// RUN: %libomp-compile-and-run
+
+/*
+ GCC failed this test because __kmp_get_gtid() instead of __kmp_entry_gtid()
+ was called in xexpand(KMP_API_NAME_GOMP_TASKGROUP_START)(void).
+ __kmp_entry_gtid() will initialize the runtime of not yet done which does not
+ happen with __kmp_get_gtid().
+ */
+
+int main()
+{
+    #pragma omp taskgroup
+    { }
+
+    return 0;
+}