diff --git a/src/utils/util/resolver-pipeline/oscal-profile-resolve-merge.xsl b/src/utils/util/resolver-pipeline/oscal-profile-resolve-merge.xsl
index 89099f6f9f..2cc3b21aa0 100644
--- a/src/utils/util/resolver-pipeline/oscal-profile-resolve-merge.xsl
+++ b/src/utils/util/resolver-pipeline/oscal-profile-resolve-merge.xsl
@@ -110,10 +110,18 @@
             <back-matter>
                 <!-- Using combination logic on back matter elements. -->
                 <xsl:for-each-group select="back-matter/* | selection/back-matter/*" group-by="(@opr:id,@uuid,generate-id())[1]">
+                    <xsl:variable name="last" as="element(resource)" select="current-group()[last()]"/>
+                    <!-- The final phase needs the ability to keep unreferenced
+                            back matter items based on keep instructions, so the merge
+                            phase must preserve these items. -->
+                    <xsl:variable name="keepers" as="element(resource)*"
+                        select="current-group()[child::prop[@name='keep' and @value='always']]"/>
                     <xsl:call-template name="combine-elements">
-                        <!-- Take last one in group because of spec
-                            requirement id="req-backmatter-dupe". -->
-                        <xsl:with-param name="who" select="current-group()[last()]" as="element(resource)"/>
+                        <!-- Take last one in group because of spec requirement
+                            id="req-backmatter-dupe". -->
+                        <!-- Take last item with keep instruction, because
+                            of spec requirement id="req-backmatter-keep". -->
+                        <xsl:with-param name="who" select="$keepers[last()] | $last" as="element(resource)+"/>
                     </xsl:call-template>
                 </xsl:for-each-group>
             </back-matter>
diff --git a/src/utils/util/resolver-pipeline/testing/3_merged/merge.xspec b/src/utils/util/resolver-pipeline/testing/3_merged/merge.xspec
index d9e44c873d..a20f188339 100644
--- a/src/utils/util/resolver-pipeline/testing/3_merged/merge.xspec
+++ b/src/utils/util/resolver-pipeline/testing/3_merged/merge.xspec
@@ -494,6 +494,127 @@
                 </back-matter>
             </x:expect>
         </x:scenario>
+        <x:scenario label="Testing keep instructions: Three resources with same uuid, where">
+            <x:scenario label="1st has keep instruction and others do not">
+                <x:context>
+                    <catalog>
+                        <selection uuid="xyz-tiny_catalog">
+                            <control id="x1"><title>Control X1</title></control>
+                            <back-matter>
+                                <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                    <title>Ref BBB, first</title>
+                                    <prop name="keep" value="always"/>
+                                </resource>
+                            </back-matter>
+                        </selection>
+                        <selection uuid="xyz-tiny_catalog2">
+                            <control id="x2"><title>Control X2</title></control>
+                            <back-matter>
+                                <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                    <title>Ref BBB, second</title>
+                                </resource>
+                            </back-matter>
+                        </selection>
+                        <back-matter>
+                            <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                <title>Ref BBB, third</title>
+                            </resource>
+                        </back-matter>
+                    </catalog>
+                </x:context>
+                <x:call template="combine-back-matter"/>
+                <x:expect label="back-matter with 1st and 3rd items. 2nd item was superseded by 3rd item.">
+                    <back-matter>
+                        <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                            <title>Ref BBB, first</title>
+                            <prop name="keep" value="always"/>
+                        </resource>
+                        <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                            <title>Ref BBB, third</title>
+                        </resource>
+                    </back-matter>
+                </x:expect>
+            </x:scenario>
+            <x:scenario label="1st and 3rd have keep instruction and 2nd does not">
+                <x:context>
+                    <catalog>
+                        <selection uuid="xyz-tiny_catalog">
+                            <control id="x1"><title>Control X1</title></control>
+                            <back-matter>
+                                <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                    <title>Ref BBB, first</title>
+                                    <prop name="keep" value="always"/>
+                                </resource>
+                            </back-matter>
+                        </selection>
+                        <selection uuid="xyz-tiny_catalog2">
+                            <control id="x2"><title>Control X2</title></control>
+                            <back-matter>
+                                <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                    <title>Ref BBB, second</title>
+                                </resource>
+                            </back-matter>
+                        </selection>
+                        <back-matter>
+                            <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                <title>Ref BBB, third</title>
+                                <prop name="keep" value="always"/>
+                            </resource>
+                        </back-matter>
+                    </catalog>
+                </x:context>
+                <x:call template="combine-back-matter"/>
+                <x:expect label="back-matter with last item only.">
+                    <back-matter>
+                        <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                            <title>Ref BBB, third</title>
+                            <prop name="keep" value="always"/>
+                        </resource>
+                    </back-matter>
+                </x:expect>
+            </x:scenario>
+            <x:scenario label="1st and 2nd have keep instruction and 3rd does not">
+                <x:context>
+                    <catalog>
+                        <selection uuid="xyz-tiny_catalog">
+                            <control id="x1"><title>Control X1</title></control>
+                            <back-matter>
+                                <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                    <title>Ref BBB, first</title>
+                                    <prop name="keep" value="always"/>
+                                </resource>
+                            </back-matter>
+                        </selection>
+                        <selection uuid="xyz-tiny_catalog2">
+                            <control id="x2"><title>Control X2</title></control>
+                            <back-matter>
+                                <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                    <title>Ref BBB, second</title>
+                                    <prop name="keep" value="always"/>
+                                </resource>
+                            </back-matter>
+                        </selection>
+                        <back-matter>
+                            <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                                <title>Ref BBB, third</title>
+                            </resource>
+                        </back-matter>
+                    </catalog>
+                </x:context>
+                <x:call template="combine-back-matter"/>
+                <x:expect label="back-matter with 2nd and 3rd items. 1st item was superseded by 2nd item.">
+                    <back-matter>
+                        <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                            <title>Ref BBB, second</title>
+                            <prop name="keep" value="always"/>
+                        </resource>
+                        <resource uuid="0050231f-4fd0-43d6-8fa0-431367cd83e2">
+                            <title>Ref BBB, third</title>
+                        </resource>
+                    </back-matter>
+                </x:expect>
+            </x:scenario>
+        </x:scenario>
         <x:scenario label="No back matter in input context">
             <x:context>
                 <catalog>