diff --git a/emle/emle.py b/emle/emle.py
index 6f58365..b7dc821 100644
--- a/emle/emle.py
+++ b/emle/emle.py
@@ -568,7 +568,7 @@ def __init__(
             # Split the module and function names.
             try:
                 function = external_backend.split(".")[-1]
-                module = external_backend.strip("." + function)
+                module = external_backend.replace("." + function, "")
             except:
                 raise ValueError(
                     f"Unable to parse 'external_backend' callback string: {external_backend}"
diff --git a/tests/input/external.py b/tests/input/external.py
index 8f86f9d..d2244fa 100644
--- a/tests/input/external.py
+++ b/tests/input/external.py
@@ -4,7 +4,7 @@
 EV_TO_HARTREE = 1.0 / ase.units.Hartree
 
 
-def run_xtb(atoms):
+def run_external(atoms):
     """
     Internal function to compute in vacuo energies and gradients using
     the xtb-python interface. Currently only uses the "GFN2-xTB" method.
diff --git a/tests/test_external.py b/tests/test_external.py
index 8d20106..773cfc7 100644
--- a/tests/test_external.py
+++ b/tests/test_external.py
@@ -37,7 +37,7 @@ def test_external_local_directory():
 
         # Set environment variables.
         os.environ["EMLE_PORT"] = "12345"
-        os.environ["EMLE_EXTERNAL_BACKEND"] = "external.run_xtb"
+        os.environ["EMLE_EXTERNAL_BACKEND"] = "external.run_external"
 
         # Create the sander command.
         command = "sander -O -i emle_sp.in -p adp.parm7 -c adp.rst7 -o emle.out"
@@ -70,7 +70,7 @@ def test_external_plugin_directory():
 
         # Set environment variables.
         os.environ["EMLE_PORT"] = "12345"
-        os.environ["EMLE_EXTERNAL_BACKEND"] = "external.run_xtb"
+        os.environ["EMLE_EXTERNAL_BACKEND"] = "external.run_external"
         os.environ["EMLE_PLUGIN_PATH"] = os.getcwd() + "/tests/input"
 
         # Create the sander command.