diff --git a/sdk/lib/opentelemetry/sdk/internal.rb b/sdk/lib/opentelemetry/sdk/internal.rb
index a088e65aef..9c9068b93e 100644
--- a/sdk/lib/opentelemetry/sdk/internal.rb
+++ b/sdk/lib/opentelemetry/sdk/internal.rb
@@ -13,15 +13,19 @@ module Internal
       extend self
 
       def boolean?(value)
-        value.is_a?(TrueClass) || value.is_a?(FalseClass)
+        value.instance_of?(TrueClass) || value.instance_of?(FalseClass)
       end
 
       def valid_key?(key)
         key.instance_of?(String)
       end
 
+      def numeric?(value)
+        value.instance_of?(Integer) || value.instance_of?(Float)
+      end
+
       def valid_simple_value?(value)
-        value.instance_of?(String) || value == false || value == true || value.is_a?(Numeric)
+        value.instance_of?(String) || boolean?(value) || numeric?(value)
       end
 
       def valid_array_value?(value)
@@ -34,7 +38,7 @@ def valid_array_value?(value)
         when TrueClass, FalseClass
           value.all? { |v| boolean?(v) }
         when Numeric
-          value.all? { |v| v.is_a?(Numeric) }
+          value.all? { |v| numeric?(v) }
         else
           false
         end
diff --git a/sdk/test/opentelemetry/sdk/trace/span_test.rb b/sdk/test/opentelemetry/sdk/trace/span_test.rb
index 5998a5ef33..dfe9cb3f41 100644
--- a/sdk/test/opentelemetry/sdk/trace/span_test.rb
+++ b/sdk/test/opentelemetry/sdk/trace/span_test.rb
@@ -105,6 +105,23 @@
       end
     end
 
+    it 'reports an error for a non-standard library Numeric subclass, which is invalid' do
+      OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+        numeric_klass = Class.new(Numeric) {}
+        span.set_attribute('foo', numeric_klass.new)
+        span.finish
+        _(log_stream.string).must_match(/invalid span attribute value type #<Class(.*)for key 'foo' on span 'name'/)
+      end
+    end
+
+    it 'reports an error for a NilClass value, which is invalid' do
+      OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+        span.set_attribute('foo', nil)
+        span.finish
+        _(log_stream.string).must_match(/invalid span attribute value type NilClass for key 'foo' on span 'name'/)
+      end
+    end
+
     it 'reports an error for an invalid key' do
       OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
         span.set_attribute(nil, 'bar')
@@ -165,6 +182,14 @@
       _(events.first.attributes).must_equal(attrs)
     end
 
+    it 'does not keep nil-valued attributes' do
+      attrs = { 'foo' => nil }
+      span.add_event('added', attributes: attrs)
+      events = span.events
+      _(events.size).must_equal(1)
+      _(events.first.attributes).must_equal({})
+    end
+
     it 'accepts array-valued attributes' do
       attrs = { 'foo' => [1, 2, 3] }
       span.add_event('added', attributes: attrs)