diff --git a/core/relinker/CMakeLists.txt b/core/relinker/CMakeLists.txt
index 8a470ff52..0764e95c7 100644
--- a/core/relinker/CMakeLists.txt
+++ b/core/relinker/CMakeLists.txt
@@ -182,6 +182,8 @@ if(BUILD_TESTING)
             ${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_guest_tls.py $<TARGET_FILE:relinker>)
         add_test(NAME elf_header COMMAND ${Python3_EXECUTABLE}
             ${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_elf_header.py $<TARGET_FILE:relinker>)
+        add_test(NAME input_magic COMMAND ${Python3_EXECUTABLE}
+            ${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_input_magic.py $<TARGET_FILE:relinker>)
     else()
         message(STATUS "Python3 interpreter not found; skipping Python relinker tests")
     endif()
diff --git a/core/relinker/relinker/include/relinker/parsing/ElfReader.hpp b/core/relinker/relinker/include/relinker/parsing/ElfReader.hpp
index 85540b25d..1ed4ca889 100644
--- a/core/relinker/relinker/include/relinker/parsing/ElfReader.hpp
+++ b/core/relinker/relinker/include/relinker/parsing/ElfReader.hpp
@@ -29,6 +29,7 @@ private:
     std::uint16_t _readU16At(FileByteOffset offset) const;
     std::uint8_t _readU8At(FileByteOffset offset) const;
     std::string _resolveShdrName(std::uint32_t nameOffset, const ElfHeader& header) const;
+    std::string formatMagic() const;
 };
 
 }
diff --git a/core/relinker/relinker/src/parsing/ElfReader.cpp b/core/relinker/relinker/src/parsing/ElfReader.cpp
index 51881ae99..ba8992b17 100644
--- a/core/relinker/relinker/src/parsing/ElfReader.cpp
+++ b/core/relinker/relinker/src/parsing/ElfReader.cpp
@@ -21,6 +21,17 @@ const std::vector<std::uint8_t>& ElfReader::GetRawBytes() const {
     return _fileBuffer;
 }
 
+std::string ElfReader::formatMagic() const {
+    static constexpr char digits[] = "0123456789abcdef";
+    std::string text;
+    for (std::size_t index = 0; index < 4; ++index) {
+        if (index != 0) text += ' ';
+        text += digits[_fileBuffer[index] >> 4];
+        text += digits[_fileBuffer[index] & 0x0f];
+    }
+    return text;
+}
+
 std::uint8_t ElfReader::_readU8At(FileByteOffset fileByteOffset) const {
     if (fileByteOffset >= _fileBuffer.size()) {
         throw RelinkerException("FileByteOffset out of bounds", fileByteOffset);
@@ -60,9 +71,13 @@ ElfHeader ElfReader::ReadHeader() const {
         throw RelinkerException("File too small for ELF header");
     }
 
+    if (_fileBuffer[0] == 0x4f && _fileBuffer[1] == 0x15 && _fileBuffer[2] == 0x3d && _fileBuffer[3] == 0x1d) {
+        throw RelinkerException("The input is a SELF container, not an ELF");
+    }
+
     if (_fileBuffer[0] != 0x7f || _fileBuffer[1] != 'E' ||
         _fileBuffer[2] != 'L' || _fileBuffer[3] != 'F') {
-        throw RelinkerException("Invalid ELF magic number");
+        throw RelinkerException("Invalid ELF magic number: " + formatMagic());
     }
 
     ElfHeader header{};
diff --git a/core/relinker/relinker/tests/test_input_magic.py b/core/relinker/relinker/tests/test_input_magic.py
new file mode 100644
index 000000000..348df5b15
--- /dev/null
+++ b/core/relinker/relinker/tests/test_input_magic.py
@@ -0,0 +1,29 @@
+"""Reject inputs that are not plain ELF files with a message that names what was read."""
+
+from pathlib import Path
+import subprocess
+import sys
+import tempfile
+
+
+def main():
+    relinker = Path(sys.argv[1]).resolve()
+    with tempfile.TemporaryDirectory(prefix="anyps5-magic-") as directory:
+        work = Path(directory)
+
+        def convert(name, content, error):
+            source = work / name
+            source.write_bytes(content)
+            output = work / (name + ".out")
+            result = subprocess.run([str(relinker), "--skip-sce-module", str(source), str(output)],
+                                    capture_output=True, text=True, timeout=20)
+            assert result.returncode == 2 and error in result.stderr and not output.exists(), (name, result)
+
+        convert("eboot.self", b"\x4f\x15\x3d\x1d" + bytes(0x1000), "The input is a SELF container, not an ELF")
+        convert("eboot.pkg", b"\x7fCNT" + bytes(0x1000), "Invalid ELF magic number: 7f 43 4e 54")
+        convert("eboot.short", b"\x7fEL", "File too small for ELF header")
+    print("Input magic diagnostics tests passed")
+
+
+if __name__ == "__main__":
+    main()