diff --git a/ext/java/org/jruby/ext/stringio/StringIO.java b/ext/java/org/jruby/ext/stringio/StringIO.java
index 85bb955..18f0f5a 100644
--- a/ext/java/org/jruby/ext/stringio/StringIO.java
+++ b/ext/java/org/jruby/ext/stringio/StringIO.java
@@ -896,7 +896,8 @@ private IRubyObject getline(ThreadContext context, final IRubyObject rs, int lim
             int w = 0;
 
             if (limit > 0 && s + limit < e) {
-                e = getEncoding().rightAdjustCharHead(stringBytes, s, s + limit, e);
+                // a fixed-width encoding may step past a truncated last character
+                e = Math.min(e, getEncoding().rightAdjustCharHead(stringBytes, s, s + limit, e));
             }
             if (rs == context.nil) {
                 if (chomp) {
diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 4f953f6..1255096 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -1555,7 +1555,10 @@ strio_getline(struct getline_arg *arg, struct StringIO *ptr)
     e = s + RSTRING_LEN(ptr->string);
     s += ptr->pos;
     if (limit > 0 && (size_t)limit < (size_t)(e - s)) {
+	const char *const end = e;
 	e = rb_enc_right_char_head(s, s + limit, e, get_enc(ptr));
+	/* a fixed-width encoding may step past a truncated last character */
+	if (e > end) e = end;
     }
     if (NIL_P(str)) {
 	if (arg->chomp) {
diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index fd88de5..cfada6f 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -151,6 +151,17 @@ def test_gets_utf_16
     assert_nil(stringio.gets)
   end
 
+  def test_gets_limit_in_truncated_fixed_width_char
+    # 6 bytes: one UTF-32 code unit and a truncated one.  The limit
+    # falls inside the truncated unit, and the line must stop at the
+    # end of the string, not beyond it.
+    stringio = StringIO.new("abcdef".b.freeze)
+    stringio.set_encoding(Encoding::UTF_32LE)
+    assert_equal("abcdef".b, stringio.gets(5).b)
+    assert_equal(6, stringio.pos)
+    assert_nil(stringio.gets(5))
+  end
+
   def test_gets_chomp
     assert_equal(nil, StringIO.new("").gets(chomp: true))
     assert_equal("", StringIO.new("\n").gets(chomp: true))