diff --git a/src/dspeed/processing_chain.py b/src/dspeed/processing_chain.py
index ff62cdf..21bca2d 100644
--- a/src/dspeed/processing_chain.py
+++ b/src/dspeed/processing_chain.py
@@ -2632,8 +2632,10 @@ def resolve_dependencies(
                 init_kwargs = {}
                 for arg in init_args_in:
                     if not isinstance(arg, str):
-                        pass
+                        init_args.append(arg)
+                        continue
 
+                    # find and replace db values
                     for db_var in db_parser.findall(arg):
                         try:
                             db_node = db_dict
diff --git a/src/dspeed/processors/iir_filter.py b/src/dspeed/processors/iir_filter.py
index dcc3fae..994d7f3 100644
--- a/src/dspeed/processors/iir_filter.py
+++ b/src/dspeed/processors/iir_filter.py
@@ -57,7 +57,7 @@ def iir_filter(
         wf_lp:
           function: iir_filter
           module: dspeed.processors
-          args_in:
+          init_args:
             - "15*MHz"
             - 4
             - wf
@@ -138,7 +138,7 @@ def notch_filter(
         wf_notch:
           function: notch_filter
           module: dspeed.processors
-          args_in:
+          init_args:
             - "15*MHz"
             - "1.5*MHz"
             - wf
@@ -196,7 +196,7 @@ def peak_filter(
         wf_peak:
           function: peak_filter
           module: dspeed.processors
-          args_in:
+          init_args:
             - "15*MHz"
             - "1.5*MHz"
             - wf
diff --git a/src/dspeed/processors/poly_fit.py b/src/dspeed/processors/poly_fit.py
index fceaa66..86e1783 100644
--- a/src/dspeed/processors/poly_fit.py
+++ b/src/dspeed/processors/poly_fit.py
@@ -34,7 +34,18 @@ def _poly_fitter(w_in: np.ndarray, inv: np.ndarray, poly_pars: np.ndarray) -> No
 
 def poly_fit(length, deg):
     """Factory function for generating a polynomial fitter for an input of length
-    `length` to a polynomial of order `deg`."""
+    `length` to a polynomial of order `deg`.
+
+    YAML Configuration Example
+    --------------------------
+
+    .. code-block:: yaml
+
+        fit_pars:
+            function: dspeed.processors.poly_fit
+            args: ["wf_logged", "fit_pars(shape=4)"]
+            init_args: ["len(wf_logged)", 3]
+    """
 
     vals_array = np.zeros(2 * deg + 1, dtype="float64")
 
diff --git a/tests/test_processing_chain.py b/tests/test_processing_chain.py
index acca063..82e196a 100644
--- a/tests/test_processing_chain.py
+++ b/tests/test_processing_chain.py
@@ -664,3 +664,42 @@ def test_database_params(geds_raw_tbl):
         geds_raw_tbl, dsp_config=dsp_config, database={"a": 2, "c": 0}, n_entries=1
     )
     assert lh5_out["test"][0] == 3
+
+    def test_init_args(geds_raw_tbl):
+        dsp_config = {
+            "outputs": ["test"],
+            "processors": {
+                "test": {
+                    "function": "dspeed.processors.poly_fit",
+                    "args": ["waveform", "test(shape=4)"],
+                    "init_args": ["len(waveform)", 3],
+                }
+            },
+        }
+        build_dsp(geds_raw_tbl, dsp_config=dsp_config, n_entries=1)
+
+        dsp_config = {
+            "outputs": ["test"],
+            "processors": {
+                "test": {
+                    "function": "dspeed.processors.poly_fit",
+                    "args": ["waveform", "test(shape=3)"],
+                    "init_args": ["len(waveform)", 3],
+                }
+            },
+        }
+        with pytest.raises(ProcessingChainError):
+            build_dsp(geds_raw_tbl, dsp_config=dsp_config, n_entries=1)
+
+        dsp_config = {
+            "outputs": ["test"],
+            "processors": {
+                "test": {
+                    "function": "dspeed.processors.poly_fit",
+                    "args": ["waveform", "test(shape=4)"],
+                    "init_args": ["len(waveform)", "db.deg"],
+                    "defaults": {"db.deg": 3},
+                }
+            },
+        }
+        build_dsp(geds_raw_tbl, dsp_config=dsp_config, n_entries=1)