diff --git a/core/time/at_spec.rb b/core/time/at_spec.rb
index c7b8755495..1a2cfa5b28 100644
--- a/core/time/at_spec.rb
+++ b/core/time/at_spec.rb
@@ -83,7 +83,7 @@
     describe "with an argument that responds to #to_r" do
       ruby_version_is ""..."1.9" do
         it "raises a TypeError" do
-          o = mock('rational')
+          o = mock_numeric('rational')
           o.should_not_receive(:to_r)
           lambda { Time.at(o) }.should raise_error(TypeError)
         end
@@ -91,7 +91,7 @@
 
       ruby_version_is "1.9" do
         it "coerces using #to_r" do
-          o = mock('rational')
+          o = mock_numeric('rational')
           o.should_receive(:to_r).and_return(Rational(5, 2))
           Time.at(o).should == Time.at(Rational(5, 2))
         end
@@ -134,7 +134,7 @@
 
     ruby_version_is "1.9" do
       it "coerces using #to_r" do
-        o = mock('rational')
+        o = mock_numeric('rational')
         o.should_receive(:to_r).and_return(Rational(5, 2))
         Time.at(0, o).should == Time.at(0, Rational(5, 2))
       end
@@ -160,12 +160,9 @@
       end
     end
 
-    ruby_version_is "1.9" do
-      it "returns a Time object equal to the specified time plus the number of microseconds" do
-        t1 = Time.at(10)
-        t2 = Time.at(t1, 500000)
-        t2.tv_sec.should == 10
-        t2.tv_usec.should == 500000
+    ruby_bug "#8173", "2.0" do
+      it "raises a TypeError" do
+        lambda { Time.at(Time.now, 500000) }.should raise_error(TypeError)
       end
     end
   end
diff --git a/core/time/getlocal_spec.rb b/core/time/getlocal_spec.rb
index f7beae2bec..4883b17a00 100644
--- a/core/time/getlocal_spec.rb
+++ b/core/time/getlocal_spec.rb
@@ -35,7 +35,7 @@
 
     describe "with an argument that responds to #to_r" do
       it "coerces using #to_r" do
-        o = mock('rational')
+        o = mock_numeric('rational')
         o.should_receive(:to_r).and_return(Rational(7201, 2))
         t = Time.gm(2007, 1, 9, 12, 0, 0).getlocal(o)
         t.should == Time.new(2007, 1, 9, 13, 0, Rational(1, 2), Rational(7201, 2))
diff --git a/core/time/localtime_spec.rb b/core/time/localtime_spec.rb
index 1d8f6162b8..b9273cd5fa 100644
--- a/core/time/localtime_spec.rb
+++ b/core/time/localtime_spec.rb
@@ -44,7 +44,7 @@
 
     describe "with an argument that responds to #to_r" do
       it "coerces using #to_r" do
-        o = mock('rational')
+        o = mock_numeric('rational')
         o.should_receive(:to_r).and_return(Rational(7201, 2))
         t = Time.gm(2007, 1, 9, 12, 0, 0)
         t.localtime(o)
diff --git a/core/time/minus_spec.rb b/core/time/minus_spec.rb
index 2920733bfc..90894fc6d3 100644
--- a/core/time/minus_spec.rb
+++ b/core/time/minus_spec.rb
@@ -23,7 +23,7 @@
   ruby_version_is "1.9" do
     #see [ruby-dev:38446]
     it "accepts arguments that can be coerced into Rational" do
-      (obj = mock('10')).should_receive(:to_r).and_return(Rational(10))
+      (obj = mock_numeric('10')).should_receive(:to_r).and_return(Rational(10))
       (Time.at(100) - obj).should == Time.at(90)
     end
   end
diff --git a/core/time/new_spec.rb b/core/time/new_spec.rb
index 297dca6a52..cea1452801 100644
--- a/core/time/new_spec.rb
+++ b/core/time/new_spec.rb
@@ -37,7 +37,7 @@
 
     describe "with an argument that responds to #to_r" do
       it "coerces using #to_r" do
-        o = mock('rational')
+        o = mock_numeric('rational')
         o.should_receive(:to_r).and_return(Rational(5, 2))
         Time.new(2000, 1, 1, 0, 0, 0, o).utc_offset.should eql(Rational(5, 2))
       end
diff --git a/core/time/plus_spec.rb b/core/time/plus_spec.rb
index 7442c07691..d835eabcde 100644
--- a/core/time/plus_spec.rb
+++ b/core/time/plus_spec.rb
@@ -65,7 +65,7 @@
     end
 
     it "accepts arguments that can be coerced into Rational" do
-      (obj = mock('10')).should_receive(:to_r).and_return(Rational(10))
+      (obj = mock_numeric('10')).should_receive(:to_r).and_return(Rational(10))
       (Time.at(100) + obj).should == Time.at(110)
     end