diff -r ab6f520f3637 Lib/test/test_warnings/__init__.py
--- a/Lib/test/test_warnings/__init__.py	Mon Sep 21 01:11:26 2015 -0400
+++ b/Lib/test/test_warnings/__init__.py	Mon Sep 21 21:20:32 2015 +0300
@@ -334,7 +334,7 @@ class WarnTests(BaseTest):
 
                 warning_tests.inner("spam7", stacklevel=9999)
                 self.assertEqual(os.path.basename(w[-1].filename),
-                                    "sys")
+                                    "runpy.py")
 
     def test_stacklevel_import(self):
         # Issue #24305: With stacklevel=2, module-level warnings should work.
diff -r ab6f520f3637 Lib/warnings.py
--- a/Lib/warnings.py	Mon Sep 21 01:11:26 2015 -0400
+++ b/Lib/warnings.py	Mon Sep 21 21:20:32 2015 +0300
@@ -188,17 +188,21 @@ def warn(message, category=None, stackle
                         "not '{:s}'".format(type(category).__name__))
     # Get context information
     try:
-        if stacklevel <= 1 or _is_internal_frame(sys._getframe(1)):
+        frame = sys._getframe(1)
+        if stacklevel <= 1 or _is_internal_frame(frame):
             # If frame is too small to care or if the warning originated in
             # internal code, then do not try to hide any frames.
-            frame = sys._getframe(stacklevel)
+            for x in range(stacklevel-1):
+                if frame.f_back is None:
+                    break
+                frame = frame.f_back
         else:
-            frame = sys._getframe(1)
             # Look for one frame less since the above line starts us off.
             for x in range(stacklevel-1):
-                frame = _next_external_frame(frame)
-                if frame is None:
-                    raise ValueError
+                f_back = _next_external_frame(frame)
+                if f_back is None:
+                    break
+                frame = f_back
     except ValueError:
         globals = sys.__dict__
         lineno = 1
diff -r ab6f520f3637 Python/_warnings.c
--- a/Python/_warnings.c	Mon Sep 21 01:11:26 2015 -0400
+++ b/Python/_warnings.c	Mon Sep 21 21:20:32 2015 +0300
@@ -583,14 +583,20 @@ setup_context(Py_ssize_t stack_level, Py
     PyFrameObject *f = PyThreadState_GET()->frame;
     // Stack level comparisons to Python code is off by one as there is no
     // warnings-related stack level to avoid.
-    if (stack_level <= 0 || is_internal_frame(f)) {
-        while (--stack_level > 0 && f != NULL) {
-            f = f->f_back;
+    if (stack_level > 0 && f != NULL) {
+        if (is_internal_frame(f)) {
+            while (stack_level > 1 && f->f_back != NULL) {
+                f = f->f_back;
+                stack_level--;
+            }
         }
-    }
-    else {
-        while (--stack_level > 0 && f != NULL) {
-            f = next_external_frame(f);
+        else {
+            PyFrameObject *f_back;
+            while (stack_level > 1 &&
+                   (f_back = next_external_frame(f)) != NULL) {
+                f = f_back;
+                stack_level--;
+            }
         }
     }