diff --git a/azure-pipelines/e2e-assets/ci-skipped-ports/always-built/portfile.cmake b/azure-pipelines/e2e-assets/ci-skipped-ports/always-built/portfile.cmake
new file mode 100644
index 0000000000..065116c276
--- /dev/null
+++ b/azure-pipelines/e2e-assets/ci-skipped-ports/always-built/portfile.cmake
@@ -0,0 +1 @@
+set(VCPKG_POLICY_EMPTY_PACKAGE enabled)
diff --git a/azure-pipelines/e2e-assets/ci-skipped-ports/always-built/vcpkg.json b/azure-pipelines/e2e-assets/ci-skipped-ports/always-built/vcpkg.json
new file mode 100644
index 0000000000..a8d6124d05
--- /dev/null
+++ b/azure-pipelines/e2e-assets/ci-skipped-ports/always-built/vcpkg.json
@@ -0,0 +1,4 @@
+{
+  "name": "always-built",
+  "version": "1.0.0"
+}
diff --git a/azure-pipelines/e2e-assets/ci-skipped-ports/always-cascade/portfile.cmake b/azure-pipelines/e2e-assets/ci-skipped-ports/always-cascade/portfile.cmake
new file mode 100644
index 0000000000..5b496536eb
--- /dev/null
+++ b/azure-pipelines/e2e-assets/ci-skipped-ports/always-cascade/portfile.cmake
@@ -0,0 +1 @@
+message(FATAL_ERROR "This port should always cascade and should not be attempted.")
diff --git a/azure-pipelines/e2e-assets/ci-skipped-ports/always-cascade/vcpkg.json b/azure-pipelines/e2e-assets/ci-skipped-ports/always-cascade/vcpkg.json
new file mode 100644
index 0000000000..63e37606f6
--- /dev/null
+++ b/azure-pipelines/e2e-assets/ci-skipped-ports/always-cascade/vcpkg.json
@@ -0,0 +1,7 @@
+{
+  "name": "always-cascade",
+  "version": "1.0.0",
+  "dependencies": [
+    "always-skip"
+  ]
+}
diff --git a/azure-pipelines/e2e-assets/ci-skipped-ports/always-skip/portfile.cmake b/azure-pipelines/e2e-assets/ci-skipped-ports/always-skip/portfile.cmake
new file mode 100644
index 0000000000..934efc9642
--- /dev/null
+++ b/azure-pipelines/e2e-assets/ci-skipped-ports/always-skip/portfile.cmake
@@ -0,0 +1 @@
+message(FATAL_ERROR "This port should always be skipped by baseline.txt and should not be attempted.")
diff --git a/azure-pipelines/e2e-assets/ci-skipped-ports/always-skip/vcpkg.json b/azure-pipelines/e2e-assets/ci-skipped-ports/always-skip/vcpkg.json
new file mode 100644
index 0000000000..9c420d0e7b
--- /dev/null
+++ b/azure-pipelines/e2e-assets/ci-skipped-ports/always-skip/vcpkg.json
@@ -0,0 +1,7 @@
+{
+  "name": "always-skip",
+  "version": "1.0.0",
+  "dependencies": [
+    "always-built"
+  ]
+}
diff --git a/azure-pipelines/e2e-assets/ci-skipped-ports/baseline.txt b/azure-pipelines/e2e-assets/ci-skipped-ports/baseline.txt
new file mode 100644
index 0000000000..cc7e6a4907
--- /dev/null
+++ b/azure-pipelines/e2e-assets/ci-skipped-ports/baseline.txt
@@ -0,0 +1,5 @@
+always-skip:arm64-osx=skip
+always-skip:x64-linux=skip
+always-skip:x64-osx=skip
+always-skip:x64-windows=skip
+always-skip:x86-windows=skip
diff --git a/azure-pipelines/end-to-end-tests-dir/ci.ps1 b/azure-pipelines/end-to-end-tests-dir/ci.ps1
index a6703b0dc6..85f60548c6 100644
--- a/azure-pipelines/end-to-end-tests-dir/ci.ps1
+++ b/azure-pipelines/end-to-end-tests-dir/ci.ps1
@@ -93,6 +93,27 @@ SUMMARY FOR $Triplet
   UNSUPPORTED: 1
 "@
 
+# test that skipped ports aren't "put back" by downstream dependencies that aren't skipped
+Refresh-TestRoot
+$Output = Run-VcpkgAndCaptureOutput ci @commonArgs --x-builtin-ports-root="$PSScriptRoot/../e2e-assets/ci-skipped-ports" --binarysource=clear --ci-baseline="$PSScriptRoot/../e2e-assets/ci-skipped-ports/baseline.txt"
+Throw-IfFailed
+if (-not ($Output -match 'always-built:[^:]+:      \*:' -and $Output -match 'Building always-built:[^@]+@1\.0\.0\.\.\.')) {
+    throw 'did not attempt to build always-built'
+}
+if (-not ($Output -match 'always-skip:[^:]+: skip\n')) {
+    throw 'tried to build skipped'
+}
+# This should be statically determinable but at the moment we do not
+# if (-not ($Output -match 'always-cascade:[^:]+: cascade\n')) {
+#     throw 'tried to build cascaded'
+# }
+Throw-IfNonContains -Actual $Output -Expected @"
+SUMMARY FOR $Triplet
+  SUCCEEDED: 1
+  CASCADED_DUE_TO_MISSING_DEPENDENCIES: 1
+  EXCLUDED: 1
+"@
+
 # test that features included only by skipped ports are not included
 $xunitFile = Join-Path $TestingRoot 'xunit.xml'
 Refresh-TestRoot
diff --git a/src/vcpkg/commands.ci.cpp b/src/vcpkg/commands.ci.cpp
index 8c94c375bf..b5bf83cbc0 100644
--- a/src/vcpkg/commands.ci.cpp
+++ b/src/vcpkg/commands.ci.cpp
@@ -197,7 +197,7 @@ namespace
             }
 
             ret.report_lines.insert_or_assign(exclusion.first, fmt::format("{:>40}: {}", exclusion.first, *state));
-            ret.known.emplace(exclusion.first, known_result);
+            ret.known.insert_or_assign(exclusion.first, known_result);
         }
 
         return ret;