diff --git a/sdk_experimental/lib/opentelemetry/sdk/trace/samplers/consistent_probability_tracestate.rb b/sdk_experimental/lib/opentelemetry/sdk/trace/samplers/consistent_probability_tracestate.rb
index c008f4e6c8..2078866639 100644
--- a/sdk_experimental/lib/opentelemetry/sdk/trace/samplers/consistent_probability_tracestate.rb
+++ b/sdk_experimental/lib/opentelemetry/sdk/trace/samplers/consistent_probability_tracestate.rb
@@ -106,7 +106,7 @@ def decimal(str)
           end
 
           def generate_r(trace_id)
-            x = trace_id.unpack1('Q>', offset: 8) | 0x3
+            x = trace_id.unpack1('@8Q>') | 0x3
             64 - x.bit_length
           end
         end