diff --git a/parser.c b/parser.c
index ab49caba..699fccd9 100644
--- a/parser.c
+++ b/parser.c
@@ -1689,13 +1689,11 @@ xmlParserNsPush(xmlParserCtxtPtr ctxt, const xmlHashedString *prefix,
         oldIndex = ctxt->nsdb->defaultNsIndex;
 
         if (oldIndex != INT_MAX) {
-            if (defAttr != 0)
-                return(0);
-
             extra = &ctxt->nsdb->extra[oldIndex];
 
             if (extra->elementId == ctxt->nsdb->elementId) {
-                xmlErrAttributeDup(ctxt, NULL, BAD_CAST "xmlns");
+                if (defAttr == 0)
+                    xmlErrAttributeDup(ctxt, NULL, BAD_CAST "xmlns");
                 return(0);
             }
 
@@ -1715,14 +1713,12 @@ xmlParserNsPush(xmlParserCtxtPtr ctxt, const xmlHashedString *prefix,
     if (oldIndex != INT_MAX) {
         extra = &ctxt->nsdb->extra[oldIndex];
 
-        if (defAttr != 0)
-            return(0);
-
         /*
          * Check for duplicate definitions on the same element.
          */
         if (extra->elementId == ctxt->nsdb->elementId) {
-            xmlErrAttributeDup(ctxt, BAD_CAST "xmlns", prefix->name);
+            if (defAttr == 0)
+                xmlErrAttributeDup(ctxt, BAD_CAST "xmlns", prefix->name);
             return(0);
         }
 
diff --git a/result/issue643.xml b/result/issue643.xml
new file mode 100644
index 00000000..3a5a92cc
--- /dev/null
+++ b/result/issue643.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0"?>
+<!DOCTYPE doc [
+<!ATTLIST elem xmlns CDATA #FIXED "urn:def2">
+<!ATTLIST elem xmlns:a CDATA #FIXED "urn:a2">
+]>
+<doc xmlns="urn:def" xmlns:a="urn:a">
+    <elem xmlns="urn:def2" xmlns:a="urn:a2"/>
+</doc>
diff --git a/result/issue643.xml.rde b/result/issue643.xml.rde
new file mode 100644
index 00000000..b8ca1392
--- /dev/null
+++ b/result/issue643.xml.rde
@@ -0,0 +1,8 @@
+0 10 doc 0 0
+0 1 doc 0 0
+1 14 #text 0 1 
+    
+1 1 elem 1 0
+1 14 #text 0 1 
+
+0 15 doc 0 0
diff --git a/result/issue643.xml.rdr b/result/issue643.xml.rdr
new file mode 100644
index 00000000..b8ca1392
--- /dev/null
+++ b/result/issue643.xml.rdr
@@ -0,0 +1,8 @@
+0 10 doc 0 0
+0 1 doc 0 0
+1 14 #text 0 1 
+    
+1 1 elem 1 0
+1 14 #text 0 1 
+
+0 15 doc 0 0
diff --git a/result/issue643.xml.sax b/result/issue643.xml.sax
new file mode 100644
index 00000000..85563b96
--- /dev/null
+++ b/result/issue643.xml.sax
@@ -0,0 +1,15 @@
+SAX.setDocumentLocator()
+SAX.startDocument()
+SAX.internalSubset(doc, , )
+SAX.attributeDecl(elem, xmlns, 1, 4, urn:def2, ...)
+SAX.attributeDecl(elem, xmlns:a, 1, 4, urn:a2, ...)
+SAX.externalSubset(doc, , )
+SAX.startElement(doc, xmlns='urn:def', xmlns:a='urn:a')
+SAX.characters(
+    , 5)
+SAX.startElement(elem)
+SAX.endElement(elem)
+SAX.characters(
+, 1)
+SAX.endElement(doc)
+SAX.endDocument()
diff --git a/result/issue643.xml.sax2 b/result/issue643.xml.sax2
new file mode 100644
index 00000000..cd7e5f1c
--- /dev/null
+++ b/result/issue643.xml.sax2
@@ -0,0 +1,15 @@
+SAX.setDocumentLocator()
+SAX.startDocument()
+SAX.internalSubset(doc, , )
+SAX.attributeDecl(elem, xmlns, 1, 4, urn:def2, ...)
+SAX.attributeDecl(elem, xmlns:a, 1, 4, urn:a2, ...)
+SAX.externalSubset(doc, , )
+SAX.startElementNs(doc, NULL, 'urn:def', 2, xmlns='urn:def', xmlns:a='urn:a', 0, 0)
+SAX.characters(
+    , 5)
+SAX.startElementNs(elem, NULL, 'urn:def2', 2, xmlns='urn:def2', xmlns:a='urn:a2', 0, 0)
+SAX.endElementNs(elem, NULL, 'urn:def2')
+SAX.characters(
+, 1)
+SAX.endElementNs(doc, NULL, 'urn:def')
+SAX.endDocument()
diff --git a/result/noent/issue643.xml b/result/noent/issue643.xml
new file mode 100644
index 00000000..3a5a92cc
--- /dev/null
+++ b/result/noent/issue643.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0"?>
+<!DOCTYPE doc [
+<!ATTLIST elem xmlns CDATA #FIXED "urn:def2">
+<!ATTLIST elem xmlns:a CDATA #FIXED "urn:a2">
+]>
+<doc xmlns="urn:def" xmlns:a="urn:a">
+    <elem xmlns="urn:def2" xmlns:a="urn:a2"/>
+</doc>
diff --git a/result/noent/issue643.xml.sax2 b/result/noent/issue643.xml.sax2
new file mode 100644
index 00000000..cd7e5f1c
--- /dev/null
+++ b/result/noent/issue643.xml.sax2
@@ -0,0 +1,15 @@
+SAX.setDocumentLocator()
+SAX.startDocument()
+SAX.internalSubset(doc, , )
+SAX.attributeDecl(elem, xmlns, 1, 4, urn:def2, ...)
+SAX.attributeDecl(elem, xmlns:a, 1, 4, urn:a2, ...)
+SAX.externalSubset(doc, , )
+SAX.startElementNs(doc, NULL, 'urn:def', 2, xmlns='urn:def', xmlns:a='urn:a', 0, 0)
+SAX.characters(
+    , 5)
+SAX.startElementNs(elem, NULL, 'urn:def2', 2, xmlns='urn:def2', xmlns:a='urn:a2', 0, 0)
+SAX.endElementNs(elem, NULL, 'urn:def2')
+SAX.characters(
+, 1)
+SAX.endElementNs(doc, NULL, 'urn:def')
+SAX.endDocument()
diff --git a/result/valid/ns2.xml b/result/valid/ns2.xml
index a4c30a85..beacf15d 100644
--- a/result/valid/ns2.xml
+++ b/result/valid/ns2.xml
@@ -7,5 +7,5 @@
 <!ATTLIST a:inner attr CDATA #FIXED "yes">
 ]>
 <a:outer xmlns:a="urn:namespace">
-  <a:inner/>
+  <a:inner xmlns:a="urn:namespace"/>
 </a:outer>
diff --git a/test/issue643.xml b/test/issue643.xml
new file mode 100644
index 00000000..e4efeaa5
--- /dev/null
+++ b/test/issue643.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0"?>
+<!DOCTYPE doc [
+    <!ATTLIST elem xmlns CDATA #FIXED 'urn:def2'>
+    <!ATTLIST elem xmlns:a CDATA #FIXED 'urn:a2'>
+]>
+
+<doc xmlns="urn:def" xmlns:a="urn:a">
+    <elem/>
+</doc>