diff a/src/hotspot/cpu/riscv/relocInfo_riscv.hpp b/src/hotspot/cpu/riscv/relocInfo_riscv.hpp
--- a/src/hotspot/cpu/riscv/relocInfo_riscv.hpp
+++ b/src/hotspot/cpu/riscv/relocInfo_riscv.hpp
@@ -31,11 +31,12 @@
   enum {
     // Relocations are byte-aligned.
     offset_unit        =  1,
     // 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