diff --git a/llvm/utils/release/test-release.sh b/llvm/utils/release/test-release.sh
index 5fd5f82b54479..ff8be5257e2c8 100755
--- a/llvm/utils/release/test-release.sh
+++ b/llvm/utils/release/test-release.sh
@@ -417,6 +417,10 @@ function configure_llvmCore() {
     # building itself and any selected runtimes in the second phase.
     if [ "$Phase" -lt "2" ]; then
       runtime_list=""
+      # compiler-rt builtins is needed on AIX to have a functional Phase 1 clang.
+      if [ "$System" = "AIX" ]; then
+        runtime_list="compiler-rt"
+      fi  
     else
       runtime_list="$runtimes"
     fi