diff --git a/ext/date_performance.c b/ext/date_performance.c
index ed2ce17..971b43f 100644
--- a/ext/date_performance.c
+++ b/ext/date_performance.c
@@ -301,6 +301,10 @@ rb_date_strptime(int argc, VALUE * argv, VALUE self)
   VALUE str = (argc > 0 ? argv[0] : rb_str_new2("-4712-01-01")),
         fmt = (argc > 1 ? argv[1] : DEFAULT_FORMAT),
         sg  = (argc > 2 ? argv[2] : ITALY);
+
+  Check_Type(str, T_STRING);
+  Check_Type(fmt, T_STRING);
+
   char * ps = RSTRING(str)->ptr;
   char * pf = RSTRING(fmt)->ptr;
   VALUE parts[4];
diff --git a/test/extension_test.rb b/test/extension_test.rb
index e7c2bdb..a6e9032 100644
--- a/test/extension_test.rb
+++ b/test/extension_test.rb
@@ -64,6 +64,16 @@ def test_sys_strptime
     assert_equal Date.new(1912, 6, 23), Date.sys_strptime("1912-06-23", "%Y-%m-%d")
   end
 
+  def test_strptime_str_input_handling
+    assert_raise(TypeError) { Date.strptime(19120623, '%Y%m%d') }
+    assert_raise(TypeError) { Date.strptime(nil, '%Y%m%d') }
+  end
+
+  def test_strptime_fmt_input_handling
+    assert_raise(TypeError) { Date.strptime('19120623', 12345) }
+    assert_raise(TypeError) { Date.strptime('19120623', nil) }
+  end
+
   # This falls back on Ruby's strptime on BSD systems because BSD's strptime doesn't
   # handle years before 1900.
   def test_strptime_fallback