diff --git a/ext/strscan/strscan.c b/ext/strscan/strscan.c
index 42a1f7f1ad..dd7caf91b0 100644
--- a/ext/strscan/strscan.c
+++ b/ext/strscan/strscan.c
@@ -634,7 +634,7 @@ set_registers(struct strscanner *p, size_t pos, size_t length)
     const int at = 0;
     OnigRegion *regs = &(p->regs);
     onig_region_clear(regs);
-    if (onig_region_set(regs, at, 0, 0)) return;
+    if (onig_region_resize(regs, at + 1) != 0) return;
     if (p->fixed_anchor_p) {
         regs->beg[at] = pos + p->curr;
         regs->end[at] = pos + p->curr + length;
diff --git a/test/strscan/test_stringscanner.rb b/test/strscan/test_stringscanner.rb
index 8530be3893..87b429b29b 100644
--- a/test/strscan/test_stringscanner.rb
+++ b/test/strscan/test_stringscanner.rb
@@ -1025,6 +1025,27 @@ def test_size
     assert_equal(4, s.size)
   end
 
+  def test_size_after_string_match
+    s = create_string_scanner("abc")
+    s.scan(/(a)(b)/)
+    s.scan("c")
+    assert_equal([1, []], [s.size, s.captures])
+  end
+
+  def test_size_after_getch
+    s = create_string_scanner("abc")
+    s.scan(/(a)(b)/)
+    s.getch
+    assert_equal([1, []], [s.size, s.captures])
+  end
+
+  def test_size_after_get_byte
+    s = create_string_scanner("abc")
+    s.scan(/(a)(b)/)
+    s.get_byte
+    assert_equal([1, []], [s.size, s.captures])
+  end
+
   def test_captures
     s = create_string_scanner("Timestamp: Fri Dec 12 1975 14:39")
     s.scan("Timestamp: ")