diff --git a/src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs b/src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs
index 80ba4545ff4..464d8e202b1 100644
--- a/src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs
+++ b/src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs
@@ -4580,13 +4580,20 @@ internal static IEnumerable<CompletionResult> CompleteFilename(CompletionContext
                     return CommandCompletion.EmptyCompletionResult;
                 }
 
-                var lastAst = context.RelatedAsts[^1];
-                if (lastAst.Parent is UsingStatementAst usingStatement
-                    && usingStatement.UsingStatementKind is UsingStatementKind.Module or UsingStatementKind.Assembly
-                    && lastAst.Extent.File is not null)
+                if (context.RelatedAsts != null && context.RelatedAsts.Count > 0)
                 {
-                    relativeBasePath = Directory.GetParent(lastAst.Extent.File).FullName;
-                    _ = currentPS.AddParameter("RelativeBasePath", relativeBasePath);
+                    var lastAst = context.RelatedAsts[^1];
+                    if (lastAst.Parent is UsingStatementAst usingStatement
+                        && usingStatement.UsingStatementKind is UsingStatementKind.Module or UsingStatementKind.Assembly
+                        && lastAst.Extent.File is not null)
+                    {
+                        relativeBasePath = Directory.GetParent(lastAst.Extent.File).FullName;
+                        _ = currentPS.AddParameter("RelativeBasePath", relativeBasePath);
+                    }
+                    else
+                    {
+                        relativeBasePath = context.ExecutionContext.SessionState.Internal.CurrentLocation.ProviderPath;
+                    }
                 }
                 else
                 {
diff --git a/test/powershell/Host/TabCompletion/TabCompletion.Tests.ps1 b/test/powershell/Host/TabCompletion/TabCompletion.Tests.ps1
index 046d00b442f..9582ad72074 100644
--- a/test/powershell/Host/TabCompletion/TabCompletion.Tests.ps1
+++ b/test/powershell/Host/TabCompletion/TabCompletion.Tests.ps1
@@ -4012,4 +4012,10 @@ Describe "WSMan Config Provider tab complete tests" -Tags Feature,RequireAdminOn
         # https://github.com/PowerShell/PowerShell/issues/4744
         # TODO: move to test cases above once working
     }
+
+    It "[CompletionCompleters]::CompleteFilename should not throw NullReferenceException with empty string" {
+        { [System.Management.Automation.CompletionCompleters]::CompleteFilename("") } | Should -Not -Throw
+        $result = [System.Management.Automation.CompletionCompleters]::CompleteFilename("")
+        $result | Should -Not -BeNullOrEmpty
+    }
 }