diff --git a/bolt/lib/Utils/CommandLineOpts.cpp b/bolt/lib/Utils/CommandLineOpts.cpp
--- a/bolt/lib/Utils/CommandLineOpts.cpp
+++ b/bolt/lib/Utils/CommandLineOpts.cpp
@@ -17,7 +17,12 @@
 
 namespace llvm {
 namespace bolt {
-const char *BoltRevision = LLVM_REVISION;
+const char *BoltRevision =
+#ifdef LLVM_REVISION
+    LLVM_REVISION;
+#else
+    "<unknown>";
+#endif
 }
 }