diff --git a/.github/workflows/dotnet.yml b/.github/workflows/dotnet.yml
index 710618b..e430717 100644
--- a/.github/workflows/dotnet.yml
+++ b/.github/workflows/dotnet.yml
@@ -14,7 +14,7 @@ jobs:
     steps:
       - uses: actions/checkout@v7
       - name: Setup .NET
-        uses: actions/setup-dotnet@v5
+        uses: actions/setup-dotnet@v6
         with:
           dotnet-version: |
             10.0.x
@@ -27,13 +27,13 @@ jobs:
       - name: Test on Ubuntu (no build)
         run: dotnet test --no-build --verbosity normal --configuration Release
       - name: Upload build artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: release-artifacts
           path: SanitizeFilename/bin/Release/
           retention-days: 1
       - name: Upload test artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: test-artifacts
           path: SanitizeFilenameTests/bin/Release/
@@ -51,14 +51,14 @@ jobs:
     steps:
       - uses: actions/checkout@v7
       - name: Setup .NET
-        uses: actions/setup-dotnet@v5
+        uses: actions/setup-dotnet@v6
         with:
           dotnet-version: |
             10.0.x
       - name: Restore dependencies
         run: dotnet restore
       - name: Download build artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: test-artifacts
           path: SanitizeFilenameTests/bin/Release/
@@ -70,7 +70,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: [build, test]
     steps:
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           name: release-artifacts
           path: SanitizeFilename/bin/Release/
@@ -93,7 +93,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: [build, test]
     steps:
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           name: release-artifacts
           path: SanitizeFilename/bin/Release/
diff --git a/.github/workflows/stale.yml b/.github/workflows/stale.yml
index 6736c09..9ca7111 100644
--- a/.github/workflows/stale.yml
+++ b/.github/workflows/stale.yml
@@ -18,7 +18,7 @@ jobs:
       pull-requests: write
 
     steps:
-    - uses: actions/stale@v10
+    - uses: actions/stale@v11
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         stale-issue-message: 'Stale issue message'
diff --git a/SanitizeFilename/SanitizeFilename.cs b/SanitizeFilename/SanitizeFilename.cs
index 07a8d26..56dd20f 100644
--- a/SanitizeFilename/SanitizeFilename.cs
+++ b/SanitizeFilename/SanitizeFilename.cs
@@ -245,7 +245,8 @@ private static string InternalSanitizeReservedFileNames(string filename, string
         {
             foreach (var reservedFileName in ReservedWindowsFileNames)
             {
-                filename = filename.Replace(reservedFileName, replacement, true, CultureInfo.InvariantCulture);
+                if (string.Equals(filename, reservedFileName, StringComparison.OrdinalIgnoreCase))
+                    return replacement;
             }
 
             return filename;
@@ -255,7 +256,7 @@ private static string InternalSanitizeReservedFileNamePrefix(string filename, st
         {
             foreach (var reservedFileNamePrefix in ReservedWindowsFileNamesWithExtension)
                 if (filename.StartsWith(reservedFileNamePrefix, true, CultureInfo.InvariantCulture))
-                    filename = string.Concat(replacement, filename.AsSpan(0, reservedFileNamePrefix.Length));
+                    filename = string.Concat(replacement, filename.AsSpan(reservedFileNamePrefix.Length - 1));
             return filename;
         }
 
diff --git a/SanitizeFilenameTests/FilenameTests/SanitizeFilenamesTests.cs b/SanitizeFilenameTests/FilenameTests/SanitizeFilenamesTests.cs
index f9d8ed3..d6fa609 100644
--- a/SanitizeFilenameTests/FilenameTests/SanitizeFilenamesTests.cs
+++ b/SanitizeFilenameTests/FilenameTests/SanitizeFilenamesTests.cs
@@ -22,10 +22,15 @@ public void TearDown()
         private static readonly string[] InvalidWindowsFileNames = ["invalid<filename", "invalid>filename", "invalid\"filename", "invalid/filename", "invalid\\filename", "invalid|filename", "invalid?filename", "invalid*filename",];
         private static readonly string[] ReservedWindowsFileNames = ["con", "CON", "PRN", "AUX", "NUL", "COM0", "COM1", "COM2", "COM3", "COM4", "COM5", "COM6", "COM7", "COM8", "COM9", "COM\u00B9", "COM\u00B2", "COM\u00B3", "LPT0", "LPT1", "LPT2", "LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9", "LPT\u00B9", "LPT\u00B2", "LPT\u00B3", "endingWithSpace ", "endingWithPeriod."];
 
-        private static readonly string[] ReservedWindowsFileNamePrefixUsed = ["con.txt", "CON.txt", "PRN.txt", "AUX.txt", "NUL.txt", "COM0.txt", "COM1.txt", "COM2.txt", "COM3.txt", "COM4.txt", "COM5.txt", "COM6.txt", "COM7.txt", "COM8.txt", "COM9.txt", "COM\u00B9.txt", "COM\u00B2.txt", "COM\u00B3.txt", "LPT0.txt", "LPT1.txt", "LPT2.txt", "LPT3.txt", "LPT4.txt", "LPT5.txt", "LPT6.txt", "LPT7.txt", "LPT8.txt", "LPT9.txt", "LPT\u00B9.txt", "LPT\u00B2.txt", "LPT\u00B3.txt"];
+        private static readonly string[] ReservedWindowsFileNamePrefixUsed = ["con.txt", "CON.txt", "PRN.txt", "AUX.txt", "NUL.txt", "COM0.txt", "COM1.txt", "COM2.txt", "COM3.txt", "COM4.txt", "COM5.txt", "COM6.txt", "COM7.txt", "COM8.txt", "COM9.txt", "COM\u00B9.txt", "COM\u00B2.txt", "COM\u00B3.txt", "LPT0.txt", "LPT1.txt", "LPT2.txt", "LPT3.txt", "LPT4.txt", "LPT5.txt", "LPT6.txt", "LPT7.txt", "LPT8.txt", "LPT9.txt", "LPT\u00B9.txt", "LPT\u00B2.txt", "LPT\u00B3.txt", "NUL.tar.gz", "nul.tar.gz", "CON.tar.gz"];
 
         private static readonly string[] ValidFileNames = ["validFileName"];
 
+        // Regression coverage for https://github.com/Codeuctivity/SanitizeFilename/issues/46 :
+        // reserved device names must only be sanitized when they are the whole base file name,
+        // not merely a substring anywhere within an otherwise legal name.
+        private static readonly string[] ValidFileNamesContainingReservedNamesAsSubstring = ["ICON", "ICON.txt", "FALCON", "RECON.doc", "beacon", "silicon Valley", "CONSOLE.txt", "CONSTRUCTION", "NULLABLE.cs", "AUXILIARY.doc", "COMPANY.docx", "DISCOMFORT", "ENCOMPASS", "LPTOP.txt", "COM10", "LPT10"];
+
         [Test]
         [TestCaseSource(nameof(ValidFileNames))]
         public void ShouldNotTouchASaneFilename(string validFilename)
@@ -35,6 +40,24 @@ public void ShouldNotTouchASaneFilename(string validFilename)
             Assert.That(sanitizedFilename, Is.EqualTo(validFilename));
         }
 
+        [Test]
+        [TestCaseSource(nameof(ValidFileNamesContainingReservedNamesAsSubstring))]
+        public void ShouldNotTouchFileNamesContainingReservedNamesAsSubstring(string validFilename)
+        {
+            var sanitizedFilename = validFilename.SanitizeFilename();
+
+            Assert.That(sanitizedFilename, Is.EqualTo(validFilename));
+        }
+
+        [Test]
+        [TestCase("CONfile*Name", "CONfile_Name")]
+        public void ShouldOnlyReplaceTheInvalidCharNotTheReservedNameSubstring(string invalidFilename, string expectedOutcome)
+        {
+            var sanitizedFilename = invalidFilename.SanitizeFilename();
+
+            Assert.That(sanitizedFilename, Is.EqualTo(expectedOutcome));
+        }
+
         [Test]
         [TestCase("CO*", 'N', "N")]
         public void ShouldSanitizeEdgeCase(string invalidFilename, char replacement, string expectedOutcome)