diff --git a/db/skiplist_test.cc b/db/skiplist_test.cc
index 9c70c5b..b548017 100644
--- a/db/skiplist_test.cc
+++ b/db/skiplist_test.cc
@@ -281,6 +281,9 @@ class ConcurrentTest {
   }
 };
 
+// Needed when building in C++11 mode.
+constexpr uint32_t ConcurrentTest::K;
+
 // Simple test that does single-threaded testing of the ConcurrentTest
 // scaffolding.
 TEST(SkipTest, ConcurrentWithoutThreads) {