diff --git a/ext/json/ext/generator/generator.c b/ext/json/ext/generator/generator.c
index 09fdd3a1..a04df36d 100644
--- a/ext/json/ext/generator/generator.c
+++ b/ext/json/ext/generator/generator.c
@@ -954,6 +954,10 @@ static VALUE generate_json_rescue(VALUE d, VALUE exc)
     struct generate_json_data *data = (struct generate_json_data *)d;
     fbuffer_free(data->buffer);
 
+    if (RBASIC_CLASS(exc) == rb_path2class("Encoding::UndefinedConversionError")) {
+        exc = rb_exc_new_str(eGeneratorError, rb_funcall(exc, rb_intern("message"), 0));
+    }
+
     rb_exc_raise(exc);
 
     return Qundef;
diff --git a/java/src/json/ext/Generator.java b/java/src/json/ext/Generator.java
index d818ce49..3c8247b9 100644
--- a/java/src/json/ext/Generator.java
+++ b/java/src/json/ext/Generator.java
@@ -17,6 +17,7 @@
 import org.jruby.runtime.ThreadContext;
 import org.jruby.runtime.builtin.IRubyObject;
 import org.jruby.util.ByteList;
+import org.jruby.exceptions.RaiseException;
 
 public final class Generator {
     private Generator() {
@@ -390,14 +391,19 @@ void generate(Session session, RubyString object, ByteList buffer) {
                 RuntimeInfo info = session.getInfo();
                 RubyString src;
 
-                if (object.encoding(session.getContext()) != info.utf8.get()) {
-                    src = (RubyString)object.encode(session.getContext(),
-                                                    info.utf8.get());
-                } else {
-                    src = object;
-                }
+                try {
+                    if (object.encoding(session.getContext()) != info.utf8.get()) {
+                        src = (RubyString)object.encode(session.getContext(),
+                                                        info.utf8.get());
+                    } else {
+                        src = object;
+                    }
 
-                session.getStringEncoder().encode(src.getByteList(), buffer);
+                    session.getStringEncoder().encode(src.getByteList(), buffer);
+                } catch (RaiseException re) {
+                  throw Utils.newException(session.getContext(), Utils.M_GENERATOR_ERROR,
+                   re.getMessage());
+                }
             }
         };
 
diff --git a/lib/json/pure/generator.rb b/lib/json/pure/generator.rb
index 0a563813..0a5c7856 100644
--- a/lib/json/pure/generator.rb
+++ b/lib/json/pure/generator.rb
@@ -347,7 +347,11 @@ def generate(obj)
         if Regexp.method_defined?(:match?)
           private def fast_serialize_string(string, buf) # :nodoc:
             buf << '"'
-            string = string.encode(::Encoding::UTF_8) unless string.encoding == ::Encoding::UTF_8
+            begin
+              string = string.encode(::Encoding::UTF_8) unless string.encoding == ::Encoding::UTF_8
+            rescue Encoding::UndefinedConversionError => error
+              raise GeneratorError, error.message
+            end
             raise GeneratorError, "source sequence is illegal/malformed utf-8" unless string.valid_encoding?
 
             if /["\\\x0-\x1f]/n.match?(string)
@@ -536,7 +540,11 @@ def to_json(state = nil, *args)
               end
               string = self
             else
-              string = encode(::Encoding::UTF_8)
+              begin
+                string = encode(::Encoding::UTF_8)
+              rescue Encoding::UndefinedConversionError => error
+                raise GeneratorError, error.message
+              end
             end
             if state.ascii_only?
               %("#{JSON.utf8_to_json_ascii(string, state.script_safe)}")
diff --git a/test/json/json_generator_test.rb b/test/json/json_generator_test.rb
index f30f9cf4..c829e44c 100755
--- a/test/json/json_generator_test.rb
+++ b/test/json/json_generator_test.rb
@@ -470,12 +470,20 @@ def test_invalid_encoding_string
     end
     assert_includes error.message, "source sequence is illegal/malformed utf-8"
 
-    assert_raise(Encoding::UndefinedConversionError) do
+    assert_raise(JSON::GeneratorError) do
+      JSON.dump("\x82\xAC\xEF".b)
+    end
+
+    assert_raise(JSON::GeneratorError) do
       "\x82\xAC\xEF".b.to_json
     end
 
-    assert_raise(Encoding::UndefinedConversionError) do
-      JSON.dump("\x82\xAC\xEF".b)
+    assert_raise(JSON::GeneratorError) do
+      ["\x82\xAC\xEF".b].to_json
+    end
+
+    assert_raise(JSON::GeneratorError) do
+      { foo: "\x82\xAC\xEF".b }.to_json
     end
   end