diff --git a/ext/re2/re2.cc b/ext/re2/re2.cc
index 41d5341..7372d85 100644
--- a/ext/re2/re2.cc
+++ b/ext/re2/re2.cc
@@ -1251,7 +1251,13 @@ static VALUE re2_regexp_scan(VALUE self, VALUE text) {
   c->input = new(nothrow) re2::StringPiece(StringValuePtr(text));
   c->regexp = self;
   c->text = text;
-  c->number_of_capturing_groups = p->pattern->NumberOfCapturingGroups();
+
+  if (p->pattern->ok()) {
+    c->number_of_capturing_groups = p->pattern->NumberOfCapturingGroups();
+  } else {
+    c->number_of_capturing_groups = 0;
+  }
+
   c->eof = false;
 
   return scanner;
diff --git a/spec/re2/scanner_spec.rb b/spec/re2/scanner_spec.rb
index 89fddf1..b0d1744 100644
--- a/spec/re2/scanner_spec.rb
+++ b/spec/re2/scanner_spec.rb
@@ -45,6 +45,12 @@
       expect(scanner.scan).to be_nil
     end
 
+    it "returns nil if the regexp is invalid" do
+      r = RE2::Regexp.new('???', :log_errors => false)
+      scanner = r.scan("Foo bar")
+      expect(scanner.scan).to be_nil
+    end
+
     it "returns an empty array if the input is empty" do
       r = RE2::Regexp.new("")
       scanner = r.scan("")