diff --git a/llvm/lib/CAS/CMakeLists.txt b/llvm/lib/CAS/CMakeLists.txt
index aad77dce370d8..b03895cfc77d7 100644
--- a/llvm/lib/CAS/CMakeLists.txt
+++ b/llvm/lib/CAS/CMakeLists.txt
@@ -1,3 +1,7 @@
+if (UNIX AND "${CMAKE_SYSTEM_NAME}" MATCHES "AIX")
+  set(additional_libs bsd)
+endif()
+
 add_llvm_component_library(LLVMCAS
   ActionCache.cpp
   ActionCaches.cpp
@@ -20,6 +24,7 @@ add_llvm_component_library(LLVMCAS
 
   LINK_LIBS
   ${LLVM_PTHREAD_LIB}
+  ${additional_libs}
 
   LINK_COMPONENTS
   Support