diff -r de5f5648be2d Python/pystate.c
--- a/Python/pystate.c	Tue Mar 15 17:24:13 2016 +0100
+++ b/Python/pystate.c	Tue Mar 15 17:56:04 2016 +0100
@@ -807,6 +807,8 @@ PyGILState_Ensure(void)
 {
     int current;
     PyThreadState *tcur;
+    int need_init_threads = 0;
+
     /* Note that we do not auto-init Python here - apart from
        potential races with 2 threads auto-initializing, pep-311
        spells out other issues.  Embedders are expected to have
@@ -815,10 +817,7 @@ PyGILState_Ensure(void)
     assert(autoInterpreterState); /* Py_Initialize() hasn't been called! */
     tcur = (PyThreadState *)PyThread_get_key_value(autoTLSkey);
     if (tcur == NULL) {
-        /* At startup, Python has no concrete GIL. If PyGILState_Ensure() is
-           called from a new thread for the first time, we need the create the
-           GIL. */
-        PyEval_InitThreads();
+        need_init_threads = 1;
 
         /* Create a new thread state for this thread */
         tcur = PyThreadState_New(autoInterpreterState);
@@ -831,6 +830,7 @@ PyGILState_Ensure(void)
     }
     else
         current = PyThreadState_IsCurrent(tcur);
+
     if (current == 0)
         PyEval_RestoreThread(tcur);
     /* Update our counter in the thread-state - no need for locks:
@@ -839,6 +839,14 @@ PyGILState_Ensure(void)
          to modify this value
     */
     ++tcur->gilstate_counter;
+
+    if (need_init_threads) {
+        /* At startup, Python has no concrete GIL. If PyGILState_Ensure() is
+           called from a new thread for the first time, we need the create the
+           GIL. */
+        PyEval_InitThreads();
+    }
+
     return current ? PyGILState_LOCKED : PyGILState_UNLOCKED;
 }