diff --git a/src/ruby/lib/grpc/generic/rpc_server.rb b/src/ruby/lib/grpc/generic/rpc_server.rb
index 3375fcf20ac..424719304e6 100644
--- a/src/ruby/lib/grpc/generic/rpc_server.rb
+++ b/src/ruby/lib/grpc/generic/rpc_server.rb
@@ -468,10 +468,11 @@ module GRPC
         route = "/#{cls.service_name}/#{name}".to_sym
         fail "already registered: rpc #{route} from #{spec}" if specs.key? route
         specs[route] = spec
+        rpc_name = GenericService.underscore(name.to_s).to_sym
         if service.is_a?(Class)
-          handlers[route] = cls.new.method(name.to_s.underscore.to_sym)
+          handlers[route] = cls.new.method(rpc_name)
         else
-          handlers[route] = service.method(name.to_s.underscore.to_sym)
+          handlers[route] = service.method(rpc_name)
         end
         logger.info("handling #{route} with #{handlers[route]}")
       end
diff --git a/src/ruby/lib/grpc/generic/service.rb b/src/ruby/lib/grpc/generic/service.rb
index 69076b4c6e8..8ea2c82f171 100644
--- a/src/ruby/lib/grpc/generic/service.rb
+++ b/src/ruby/lib/grpc/generic/service.rb
@@ -30,24 +30,6 @@
 require 'grpc/generic/client_stub'
 require 'grpc/generic/rpc_desc'
 
-# Extend String to add a method underscore
-class String
-  # creates a new string that is the underscore separate version of this one.
-  #
-  # E.g,
-  # PrintHTML -> print_html
-  # AMethod -> a_method
-  # AnRpc -> an_rpc
-  def underscore
-    word = dup
-    word.gsub!(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
-    word.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
-    word.tr!('-', '_')
-    word.downcase!
-    word
-  end
-end
-
 # GRPC contains the General RPC module.
 module GRPC
   # Provides behaviour used to implement schema-derived service classes.
@@ -55,6 +37,22 @@ module GRPC
   # Is intended to be used to support both client and server
   # IDL-schema-derived servers.
   module GenericService
+    # creates a new string that is the underscore separate version of s.
+    #
+    # E.g,
+    # PrintHTML -> print_html
+    # AMethod -> a_method
+    # AnRpc -> an_rpc
+    #
+    # @param s [String] the string to be converted.
+    def self.underscore(s)
+      s.gsub!(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
+      s.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
+      s.tr!('-', '_')
+      s.downcase!
+      s
+    end
+
     # Used to indicate that a name has already been specified
     class DuplicateRpcName < StandardError
       def initialize(name)
@@ -171,7 +169,7 @@ module GRPC
           # Used define_method to add a method for each rpc_desc.  Each method
           # calls the base class method for the given descriptor.
           descs.each_pair do |name, desc|
-            mth_name = name.to_s.underscore.to_sym
+            mth_name = GenericService.underscore(name.to_s).to_sym
             marshal = desc.marshal_proc
             unmarshal = desc.unmarshal_proc(:output)
             route = "/#{route_prefix}/#{name}"
@@ -207,7 +205,7 @@ module GRPC
       # implemented.
       def assert_rpc_descs_have_methods
         rpc_descs.each_pair do |m, spec|
-          mth_name = m.to_s.underscore.to_sym
+          mth_name = GenericService.underscore(m.to_s).to_sym
           unless instance_methods.include?(mth_name)
             fail "#{self} does not provide instance method '#{mth_name}'"
           end
diff --git a/src/ruby/spec/generic/service_spec.rb b/src/ruby/spec/generic/service_spec.rb
index e7f5a65d3b3..6cfc34db84d 100644
--- a/src/ruby/spec/generic/service_spec.rb
+++ b/src/ruby/spec/generic/service_spec.rb
@@ -56,15 +56,6 @@ end
 GenericService = GRPC::GenericService
 Dsl = GenericService::Dsl
 
-describe 'String#underscore' do
-  it 'should convert CamelCase to underscore separated' do
-    expect('AnRPC'.underscore).to eq('an_rpc')
-    expect('AMethod'.underscore).to eq('a_method')
-    expect('PrintHTML'.underscore).to eq('print_html')
-    expect('PrintHTMLBooks'.underscore).to eq('print_html_books')
-  end
-end
-
 describe Dsl do
   it 'can be included in new classes' do
     blk = proc { Class.new { include Dsl } }
@@ -73,6 +64,15 @@ describe Dsl do
 end
 
 describe GenericService do
+  context '#underscore' do
+    it 'should convert CamelCase to underscore separated' do
+      expect(GenericService.underscore('AnRPC')).to eq('an_rpc')
+      expect(GenericService.underscore('AMethod')).to eq('a_method')
+      expect(GenericService.underscore('PrintHTML')).to eq('print_html')
+      expect(GenericService.underscore('SeeHTMLBooks')).to eq('see_html_books')
+    end
+  end
+
   describe 'including it' do
     it 'adds a class method, rpc' do
       c = Class.new do