diff --git a/include/wx/buffer.h b/include/wx/buffer.h
index 800c41b714..ec0e1fc765 100644
--- a/include/wx/buffer.h
+++ b/include/wx/buffer.h
@@ -312,6 +312,10 @@ public:
         if ( !str )
             return false;
 
+        // For consistency with the ctor taking just the length, NUL-terminate
+        // the buffer.
+        str[len] = (CharType)0;
+
         if ( this->m_data == this->GetNullData() )
         {
             this->m_data = new Data(str, len);
diff --git a/tests/strings/strings.cpp b/tests/strings/strings.cpp
index af18513045..39e1904fd6 100644
--- a/tests/strings/strings.cpp
+++ b/tests/strings/strings.cpp
@@ -1039,4 +1039,18 @@ void StringTestCase::ScopedBuffers()
     wxCharBuffer buf2 = sbuf;
     CPPUNIT_ASSERT( buf2.data() != literal );
     CPPUNIT_ASSERT_EQUAL( literal, buf.data() );
+
+    // Check that extending the buffer keeps it NUL-terminated.
+    size_t len = 10;
+
+    wxCharBuffer buf3(len);
+    CPPUNIT_ASSERT_EQUAL('\0', buf3.data()[len]);
+
+    wxCharBuffer buf4;
+    buf4.extend(len);
+    CPPUNIT_ASSERT_EQUAL('\0', buf4.data()[len]);
+
+    wxCharBuffer buf5(5);
+    buf5.extend(len);
+    CPPUNIT_ASSERT_EQUAL('\0', buf5.data()[len]);
 }