diff --git a/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetDetail.xsl b/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetDetail.xsl
index 7cdffa0d96..26c8416258 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetDetail.xsl
+++ b/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetDetail.xsl
@@ -6,7 +6,8 @@
   xmlns:marc="http://www.loc.gov/MARC21/slim"
   xmlns:items="http://www.koha-community.org/items"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  exclude-result-prefixes="marc items">
+  xmlns:str="http://exslt.org/strings"
+  exclude-result-prefixes="marc items str">
 
 <xsl:import href="UNIMARCslimUtils.xsl"/>
 <xsl:output method = "html" indent="yes" omit-xml-declaration = "yes" encoding="UTF-8"/>
diff --git a/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetResults.xsl b/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetResults.xsl
index a6ba1c22c6..7155e16cdb 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetResults.xsl
+++ b/koha-tmpl/intranet-tmpl/prog/en/xslt/UNIMARCslim2intranetResults.xsl
@@ -7,7 +7,9 @@
   xmlns:marc="http://www.loc.gov/MARC21/slim"
   xmlns:items="http://www.koha-community.org/items"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  exclude-result-prefixes="marc items">
+  xmlns:str="http://exslt.org/strings"
+  exclude-result-prefixes="marc items str">
+
 <xsl:import href="UNIMARCslimUtils.xsl"/>
 <xsl:output method = "html" indent="yes" omit-xml-declaration = "yes" encoding="UTF-8"/>
 <xsl:key name="item-by-status" match="items:item" use="items:status"/>
diff --git a/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACDetail.xsl b/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACDetail.xsl
index 8cb8bf922b..a9779b615b 100644
--- a/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACDetail.xsl
+++ b/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACDetail.xsl
@@ -6,7 +6,8 @@
   xmlns:marc="http://www.loc.gov/MARC21/slim"
   xmlns:items="http://www.koha-community.org/items"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  exclude-result-prefixes="marc items">
+  xmlns:str="http://exslt.org/strings"
+  exclude-result-prefixes="marc items str">
 
 <xsl:import href="UNIMARCslimUtils.xsl"/>
 <xsl:output method = "html" indent="yes" omit-xml-declaration = "yes" encoding="UTF-8"/>
diff --git a/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACResults.xsl b/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACResults.xsl
index 874cf99f2b..9d599f7752 100644
--- a/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACResults.xsl
+++ b/koha-tmpl/opac-tmpl/bootstrap/en/xslt/UNIMARCslim2OPACResults.xsl
@@ -6,7 +6,8 @@
   xmlns:marc="http://www.loc.gov/MARC21/slim"
   xmlns:items="http://www.koha-community.org/items"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  exclude-result-prefixes="marc items">
+  xmlns:str="http://exslt.org/strings"
+  exclude-result-prefixes="marc items str">
 
 <xsl:import href="UNIMARCslimUtils.xsl"/>
 <xsl:output method = "html" indent="yes" omit-xml-declaration = "yes" encoding="UTF-8"/>