diff a/src/hotspot/cpu/aarch64/relocInfo_aarch64.hpp b/src/hotspot/cpu/aarch64/relocInfo_aarch64.hpp
--- a/src/hotspot/cpu/aarch64/relocInfo_aarch64.hpp
+++ b/src/hotspot/cpu/aarch64/relocInfo_aarch64.hpp
@@ -32,11 +32,12 @@
     // AArch64 instructions are always 4 bytes long and 4-aligned, so
     // the two lowest offset bits can always be discarded.
     offset_unit        =  4,
     // Must be at least 1 for RelocInfo::narrow_oop_in_const.
     // Must be at least 2 for ZGC GC barrier patching.
-    format_width       =  2
+    // Must be at least 3 for Shenandoah GC barrier patching.
+    format_width       =  3
   };
 
  public:
 
   // This platform has no oops in the code that are not also