diff --git a/tests/cpp/CMakeLists.txt b/tests/cpp/CMakeLists.txt
index cf34caf81..ab82b6494 100644
--- a/tests/cpp/CMakeLists.txt
+++ b/tests/cpp/CMakeLists.txt
@@ -2,7 +2,7 @@ if(USE_DMLC_GTEST)
   if(NOT TARGET gtest)
     message(FATAL_ERROR "USE_DMLC_GTEST=ON but dmlc-core didn't bundle gtest")
   endif()
-  set(GTEST_LIBRARIES gtest)
+  set(GTEST_LIBRARIES gtest gmock)
 else()
   find_package(GTest REQUIRED)
 endif()