diff --git a/ChangeLog b/ChangeLog
index 29428ed3..5b150c27 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2012-07-14  Jay Berkenbilt  <ejb@ql.org>
+
+	* QPDFWriter: detect if the user has inserted an indirect object
+	from another QPDF object and throw an exception directing the user
+	to copyForeignObject.
+
 2012-07-11  Jay Berkenbilt  <ejb@ql.org>
 
 	* Added new APIs to copy objects from one QPDF to another.  This
diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index a7c78b19..ce5cb3e0 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -761,6 +761,15 @@ QPDFWriter::enqueueObject(QPDFObjectHandle object)
 {
     if (object.isIndirect())
     {
+        if (object.getOwningQPDF() != &(this->pdf))
+        {
+            QTC::TC("qpdf", "QPDFWriter foreign object");
+            throw std::logic_error(
+                "QPDFObjectHandle from different QPDF found while writing."
+                "  Use QPDF::copyForeignObject to add objects from"
+                " another file.");
+        }
+
 	if (object.isNull())
 	{
 	    // This is a place-holder object for an object stream
diff --git a/qpdf/qpdf.testcov b/qpdf/qpdf.testcov
index ee257faa..a570f642 100644
--- a/qpdf/qpdf.testcov
+++ b/qpdf/qpdf.testcov
@@ -233,3 +233,4 @@ QPDF not crossing page boundary 0
 QPDF replace foreign indirect with null 0
 QPDF not copying pages object 0
 QPDF insert foreign page 0
+QPDFWriter foreign object 0
diff --git a/qpdf/qtest/qpdf.test b/qpdf/qtest/qpdf.test
index fc355666..221d0a8b 100644
--- a/qpdf/qtest/qpdf.test
+++ b/qpdf/qtest/qpdf.test
@@ -149,7 +149,7 @@ $td->runtest("remove page we don't have",
 	     $td->NORMALIZE_NEWLINES);
 # ----------
 $td->notify("--- Miscellaneous Tests ---");
-$n_tests += 43;
+$n_tests += 44;
 
 $td->runtest("qpdf version",
 	     {$td->COMMAND => "qpdf --version"},
@@ -365,6 +365,10 @@ $td->runtest("reserved objects",
 $td->runtest("check output",
              {$td->FILE => "a.pdf"},
              {$td->FILE => "reserved-objects.pdf"});
+$td->runtest("detect foreign object in write",
+             {$td->COMMAND => "test_driver 29 copy-foreign-objects-in.pdf"},
+             {$td->FILE => "foreign-in-write.out", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
 
 show_ntests();
 # ----------
diff --git a/qpdf/qtest/qpdf/foreign-in-write.out b/qpdf/qtest/qpdf/foreign-in-write.out
new file mode 100644
index 00000000..14293aa9
--- /dev/null
+++ b/qpdf/qtest/qpdf/foreign-in-write.out
@@ -0,0 +1,2 @@
+logic error: QPDFObjectHandle from different QPDF found while writing.  Use QPDF::copyForeignObject to add objects from another file.
+test 29 done
diff --git a/qpdf/test_driver.cc b/qpdf/test_driver.cc
index d712d87d..4b2bc3d9 100644
--- a/qpdf/test_driver.cc
+++ b/qpdf/test_driver.cc
@@ -999,6 +999,26 @@ void runtest(int n, char const* filename)
             std::cout << "logic error: " << e.what() << std::endl;
         }
     }
+    else if (n == 29)
+    {
+        // Detect mixed objects in QPDFWriter
+        QPDF other;
+        other.processFile("minimal.pdf");
+        // Should use copyForeignObject instead
+        other.getTrailer().replaceKey(
+            "/QTest", pdf.getTrailer().getKey("/QTest"));
+
+        try
+        {
+            QPDFWriter w(other, "a.pdf");
+            w.write();
+            std::cout << "oops -- didn't throw" << std::endl;
+        }
+        catch (std::logic_error e)
+        {
+            std::cout << "logic error: " << e.what() << std::endl;
+        }
+    }
     else
     {
 	throw std::runtime_error(std::string("invalid test ") +