diff --git a/cmake/external/eigen.cmake b/cmake/external/eigen.cmake
index f7483f6be9169eb58f0148cd3a956a8c881e1fe3..bd853d921b4362ac7ac5e17e629552b2a200f08a 100644
--- a/cmake/external/eigen.cmake
+++ b/cmake/external/eigen.cmake
@@ -8,7 +8,7 @@ ExternalProject_Add(
     extern_eigen3
     ${EXTERNAL_PROJECT_LOG_ARGS}
     GIT_REPOSITORY  "https://github.com/RLovelett/eigen.git"
-    GIT_TAG         "master"
+    GIT_TAG         4e79cb69b9425f5f8c3a84be4350d4ab75b5fd9d
     PREFIX          ${EIGEN_SOURCE_DIR}
     UPDATE_COMMAND  ""
     CONFIGURE_COMMAND ""
diff --git a/cmake/external/gflags.cmake b/cmake/external/gflags.cmake
index 957f8271e4841836956b0c3f2cf3d8c88a31192a..7582292182b41e59a2012fd5db60716355d4d710 100644
--- a/cmake/external/gflags.cmake
+++ b/cmake/external/gflags.cmake
@@ -36,6 +36,7 @@ ExternalProject_Add(
     # change this back to the official Github repo once my PR is
     # merged.
     GIT_REPOSITORY  "https://github.com/wangkuiyi/gflags.git"
+    GIT_TAG         986964c07427ecb9cdb5bd73f73ebbd40e54dadb
     PREFIX          ${GFLAGS_SOURCES_DIR}
     UPDATE_COMMAND  ""
     CMAKE_ARGS      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
diff --git a/cmake/external/glog.cmake b/cmake/external/glog.cmake
index b3fef738ccc0b5886bb0a32501bb7b7adade0ff1..0d5d1e3c7ebcbdc78645547f18aaa1f8160de7d3 100644
--- a/cmake/external/glog.cmake
+++ b/cmake/external/glog.cmake
@@ -31,6 +31,7 @@ ExternalProject_Add(
     ${EXTERNAL_PROJECT_LOG_ARGS}
     DEPENDS gflags
     GIT_REPOSITORY  "https://github.com/google/glog.git"
+    GIT_TAG         v0.3.5
     PREFIX          ${GLOG_SOURCES_DIR}
     UPDATE_COMMAND  ""
     CMAKE_ARGS      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
diff --git a/cmake/external/warpctc.cmake b/cmake/external/warpctc.cmake
index bb258c7b5581fc22b44f4fe15c119f8081f4767e..638c219b9164aba4539970ba954ba00d88f86e26 100644
--- a/cmake/external/warpctc.cmake
+++ b/cmake/external/warpctc.cmake
@@ -35,6 +35,7 @@ ExternalProject_Add(
     extern_warpctc
     ${EXTERNAL_PROJECT_LOG_ARGS}
     GIT_REPOSITORY  "https://github.com/gangliao/warp-ctc.git"
+    GIT_TAG         b63a0644654a3e0ed624c85a1767bc8193aead09
     PREFIX          ${WARPCTC_SOURCES_DIR}
     UPDATE_COMMAND  ""
     CMAKE_ARGS      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}