diff --git a/Cite_body.php b/Cite_body.php
index 9daf9217f..7ec21483d 100644
--- a/Cite_body.php
+++ b/Cite_body.php
@@ -235,8 +235,14 @@ class Cite {
 					$this->mReferencesErrors[] =
 						$this->error( 'cite_error_references_missing_key', $key );
 				} else {
-					# Assign the text to corresponding ref
-					$this->mRefs[$group][$key]['text'] = $str;
+					if ( isset( $this->mRefs[$group][$key]['text'] ) && $str !== $this->mRefs[$group][$key]['text'] ) {
+						// two refs with same key and different content
+						// add error message to the original ref
+						$this->mRefs[$group][$key]['text'] .= ' ' . $this->error( 'cite_error_references_duplicate_key', $key, 'noparse' );
+					} else {
+						# Assign the text to corresponding ref
+						$this->mRefs[$group][$key]['text'] = $str;
+					}
 				}
 			} else {
 				# <ref> called in <references> has no content.
diff --git a/citeParserTests.txt b/citeParserTests.txt
index b16005961..695378c04 100644
--- a/citeParserTests.txt
+++ b/citeParserTests.txt
@@ -532,3 +532,55 @@ Page one.<ref name="the-name" follow="the-name">This ref is invalid.</ref>
 invalid names, e.g. too many</strong>
 </p>
 !! end
+
+!! test
+Multiple definition (outside <references/>)
+!! input
+<ref name=a>abc</ref>
+<ref name=a>def</ref>
+<references />
+!! result
+<p><sup id="cite_ref-a_1-0" class="reference"><a href="#cite_note-a-1">[1]</a></sup>
+<sup id="cite_ref-a_1-1" class="reference"><a href="#cite_note-a-1">[1]</a></sup>
+</p>
+<ol class="references">
+<li id="cite_note-a-1"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-a_1-0">1.0</a></sup> <sup><a href="#cite_ref-a_1-1">1.1</a></sup></span> <span class="reference-text">abc <strong class="error mw-ext-cite-error">Cite error: Invalid <code>&lt;ref&gt;</code> tag; name "a" defined multiple times with different content</strong></span>
+</li>
+</ol>
+
+!! end
+
+!! test
+Multiple definition (inside <references/>)
+!! input
+<ref name=a />
+<references>
+<ref name=a>abc</ref>
+<ref name=a>def</ref>
+</references>
+!! result
+<p><sup id="cite_ref-a_1-0" class="reference"><a href="#cite_note-a-1">[1]</a></sup>
+</p>
+<ol class="references">
+<li id="cite_note-a-1"><span class="mw-cite-backlink"><a href="#cite_ref-a_1-0">↑</a></span> <span class="reference-text">abc <strong class="error mw-ext-cite-error">Cite error: Invalid <code>&lt;ref&gt;</code> tag; name "a" defined multiple times with different content</strong></span>
+</li>
+</ol>
+
+!! end
+
+!! test
+Multiple definition (mixed outside/inside)
+!! input
+<ref name=a>abc</ref>
+<references>
+<ref name=a>def</ref>
+</references>
+!! result
+<p><sup id="cite_ref-a_1-0" class="reference"><a href="#cite_note-a-1">[1]</a></sup>
+</p>
+<ol class="references">
+<li id="cite_note-a-1"><span class="mw-cite-backlink"><a href="#cite_ref-a_1-0">↑</a></span> <span class="reference-text">abc <strong class="error mw-ext-cite-error">Cite error: Invalid <code>&lt;ref&gt;</code> tag; name "a" defined multiple times with different content</strong></span>
+</li>
+</ol>
+
+!! end