diff --git a/cle/backends/pe/pe.py b/cle/backends/pe/pe.py
index f9b72b03..25b7d57f 100644
--- a/cle/backends/pe/pe.py
+++ b/cle/backends/pe/pe.py
@@ -9,7 +9,11 @@
 
 import archinfo
 import pefile
-import pyxdia
+
+try:
+    import pyxdia
+except ImportError:
+    pyxdia = None
 
 from cle.address_translator import AT
 from cle.backends.backend import Backend, FunctionHint, FunctionHintSource, register_backend
@@ -215,6 +219,10 @@ def load_symbols_from_pdb(self, pdb_path):
         """
         Load available symbols from PDB at `pdb_path`
         """
+        if pyxdia is None:
+            log.warning("PDB support is unavailable because pyxdia is not installed")
+            return
+
         log.debug("Loading symbols from %s", pdb_path)
         try:
             pdb = pyxdia.PDB(pdb_path)
diff --git a/cle/backends/uefi_firmware.py b/cle/backends/uefi_firmware.py
index c93525d2..8301ab92 100644
--- a/cle/backends/uefi_firmware.py
+++ b/cle/backends/uefi_firmware.py
@@ -8,7 +8,11 @@
 from uuid import UUID
 
 import archinfo
-import uefi_firmware
+
+try:
+    import uefi_firmware
+except ImportError:
+    uefi_firmware = None
 
 from cle.errors import CLEUnknownFormatError
 
@@ -50,11 +54,15 @@ def _to_bytes(cls, fileobj: io.IOBase):
 
     @classmethod
     def is_compatible(cls, stream):
+        if uefi_firmware is None:
+            return False
         buffer = cls._to_bytes(stream)
         parser = uefi_firmware.AutoParser(buffer)
         return parser.type() != "unknown"
 
     def __init__(self, *args, **kwargs) -> None:
+        if uefi_firmware is None:
+            raise ImportError("The UEFI backend requires the uefi-firmware package")
         super().__init__(*args, **kwargs)
 
         # hack: we are using a loader internal method in a non-kosher way which will cause our children to be
diff --git a/pyproject.toml b/pyproject.toml
index 54985f3e..0e3f8921 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,9 +25,9 @@ dependencies = [
     "pyelftools>=0.29",
     "pyvex==9.3.1.dev0",
     "pyxbe~=1.0.3",
-    "pyxdia~=0.1",
+    "pyxdia~=0.1; sys_platform != 'emscripten'",
     "sortedcontainers>=2.0",
-    "uefi-firmware~=1.16",
+    "uefi-firmware~=1.16; sys_platform != 'emscripten'",
 ]
 
 [project.readme]