diff --git a/kernels/TIndexKernel.cpp b/kernels/TIndexKernel.cpp
index 6ee3c6af61..50c7d68538 100644
--- a/kernels/TIndexKernel.cpp
+++ b/kernels/TIndexKernel.cpp
@@ -87,7 +87,7 @@ void TIndexKernel::addSwitches(ProgramArgs& args)
     args.add("tindex", "OGR-readable/writeable tile index output",
         m_idxFilename).setPositional();
     args.add("filespec", "Build: Pattern of files to index. "
-        "Merge: Output filename", m_filespec).setPositional();
+        "Merge: Output filename", m_filespec).setOptionalPositional();
     args.add("fast_boundary", "Use extent instead of exact boundary",
         m_fastBoundary);
     args.add("lyr_name", "OGR layer name to write into datasource",
@@ -140,6 +140,9 @@ void TIndexKernel::validateSwitches(ProgramArgs& args)
     {
         if (m_filespec.empty() && !m_usestdin)
             throw pdal_error("No input pattern specified");
+        if (m_filespec.size() && m_usestdin)
+            throw pdal_error("Can't specify both --filespec and --stdin "
+                "options.");
         if (args.set("polygon"))
             throw pdal_error("'polygon' option not supported when building "
                 "index.");
diff --git a/test/unit/apps/TIndexTest.cpp b/test/unit/apps/TIndexTest.cpp
index 16310ba750..438755120b 100644
--- a/test/unit/apps/TIndexTest.cpp
+++ b/test/unit/apps/TIndexTest.cpp
@@ -82,3 +82,65 @@ TEST(TIndex, test1)
     EXPECT_NE(pos, std::string::npos);
 }
 
+TEST(TIndex, test2)
+{
+    std::string inSpec(Support::datapath("tindex/*.txt"));
+    std::string outSpec(Support::temppath("tindex.out"));
+
+    FileUtils::deleteDirectory(outSpec);
+    std::string cmd = Support::binpath("pdal") + " tindex --stdin " +
+        outSpec + " \"" + inSpec + "\" 2>&1";
+
+    std::string output;
+    Utils::run_shell_command(cmd, output);
+    std::string::size_type pos = output.find("Can't specify both");
+    EXPECT_NE(pos, std::string::npos);
+
+    cmd = Support::binpath("pdal") + " tindex --stdin " +
+        outSpec + " --filespec=\"" + inSpec + "\" 2>&1";
+    Utils::run_shell_command(cmd, output);
+    pos = output.find("Can't specify both");
+    EXPECT_NE(pos, std::string::npos);
+}
+
+// Indentical to test1, but filespec input comes from find command.
+TEST(TIndex, test3)
+{
+    std::string outSpec(Support::temppath("tindex.out"));
+    std::string outPoints(Support::temppath("points.txt"));
+
+    std::string cmd = "find " + Support::datapath("tindex") +
+        " -name \"*.txt\" | " + Support::binpath("pdal") + " tindex --stdin " +
+        outSpec;
+
+    FileUtils::deleteDirectory(outSpec);
+
+    std::string output;
+    Utils::run_shell_command(cmd, output);
+
+    cmd = Support::binpath("pdal") + " --verbose=info tindex --merge " +
+        outSpec + " " + outPoints + " --log=stdout "
+        "--bounds=\"([1.25, 3],[1.25, 3])\"";
+
+    FileUtils::deleteFile(outPoints);
+    Utils::run_shell_command(cmd, output);
+    std::string::size_type pos = output.find("Merge filecount: 3");
+    EXPECT_NE(pos, std::string::npos);
+
+    cmd = Support::binpath("pdal") + " --verbose=info tindex --merge " +
+        outSpec + " " + outPoints + " --log=stdout "
+        "--bounds=\"([1.25, 2],[1.25, 2])\"";
+    FileUtils::deleteFile(outPoints);
+    Utils::run_shell_command(cmd, output);
+    pos = output.find("Merge filecount: 2");
+    EXPECT_NE(pos, std::string::npos);
+
+    cmd = Support::binpath("pdal") + " --verbose=info tindex --merge " +
+        outSpec + " " + outPoints + " --log=stdout "
+        "--bounds=\"([1.25, 1.75],[1.25, 1.75])\"";
+    FileUtils::deleteFile(outPoints);
+    Utils::run_shell_command(cmd, output);
+    pos = output.find("Merge filecount: 1");
+    EXPECT_NE(pos, std::string::npos);
+}
+