diff --git a/invokeai/backend/image_util/hed.py b/invokeai/backend/image_util/hed.py
index 378e3b96e9..97706df8b9 100644
--- a/invokeai/backend/image_util/hed.py
+++ b/invokeai/backend/image_util/hed.py
@@ -8,7 +8,7 @@ from huggingface_hub import hf_hub_download
 from PIL import Image
 
 from invokeai.backend.image_util.util import (
-    non_maximum_suppression,
+    nms,
     normalize_image_channel_count,
     np_to_pil,
     pil_to_np,
@@ -134,7 +134,7 @@ class HEDProcessor:
         detected_map = cv2.resize(detected_map, (width, height), interpolation=cv2.INTER_LINEAR)
 
         if scribble:
-            detected_map = non_maximum_suppression(detected_map, 127, 3.0)
+            detected_map = nms(detected_map, 127, 3.0)
             detected_map = cv2.GaussianBlur(detected_map, (0, 0), 3.0)
             detected_map[detected_map > 4] = 255
             detected_map[detected_map < 255] = 0
diff --git a/invokeai/backend/image_util/util.py b/invokeai/backend/image_util/util.py
index 7cfe0ad1a5..f704f068e3 100644
--- a/invokeai/backend/image_util/util.py
+++ b/invokeai/backend/image_util/util.py
@@ -1,4 +1,5 @@
 from math import ceil, floor, sqrt
+from typing import Optional
 
 import cv2
 import numpy as np
@@ -153,10 +154,13 @@ def resize_image_to_resolution(input_image: np.ndarray, resolution: int) -> np.n
         return cv2.resize(input_image, (w, h), interpolation=cv2.INTER_AREA)
 
 
-def non_maximum_suppression(image: np.ndarray, threshold: int, sigma: float):
+def nms(np_img: np.ndarray, threshold: Optional[int] = None, sigma: Optional[float] = None) -> np.ndarray:
     """
     Apply non-maximum suppression to an image.
 
+    If both threshold and sigma are provided, the image will blurred before the suppression and thresholded afterwards,
+    resulting in a binary output image.
+
     This function is adapted from https://github.com/lllyasviel/ControlNet.
 
     Args:
@@ -166,23 +170,36 @@ def non_maximum_suppression(image: np.ndarray, threshold: int, sigma: float):
 
     Returns:
         The image after non-maximum suppression.
+
+    Raises:
+        ValueError: If only one of threshold and sigma provided.
     """
 
-    image = cv2.GaussianBlur(image.astype(np.float32), (0, 0), sigma)
+    # Raise a value error if only one of threshold and sigma is provided
+    if (threshold is None) != (sigma is None):
+        raise ValueError("Both threshold and sigma must be provided if one is provided.")
+
+    if sigma is not None and threshold is not None:
+        # Blurring the image can help to thin out features
+        np_img = cv2.GaussianBlur(np_img.astype(np.float32), (0, 0), sigma)
 
     filter_1 = np.array([[0, 0, 0], [1, 1, 1], [0, 0, 0]], dtype=np.uint8)
     filter_2 = np.array([[0, 1, 0], [0, 1, 0], [0, 1, 0]], dtype=np.uint8)
     filter_3 = np.array([[1, 0, 0], [0, 1, 0], [0, 0, 1]], dtype=np.uint8)
     filter_4 = np.array([[0, 0, 1], [0, 1, 0], [1, 0, 0]], dtype=np.uint8)
 
-    y = np.zeros_like(image)
+    nms_img = np.zeros_like(np_img)
 
     for f in [filter_1, filter_2, filter_3, filter_4]:
-        np.putmask(y, cv2.dilate(image, kernel=f) == image, image)
+        np.putmask(nms_img, cv2.dilate(np_img, kernel=f) == np_img, np_img)
 
-    z = np.zeros_like(y, dtype=np.uint8)
-    z[y > threshold] = 255
-    return z
+    if sigma is not None and threshold is not None:
+        # We blurred - now threshold to get a binary image
+        thresholded = np.zeros_like(nms_img, dtype=np.uint8)
+        thresholded[nms_img > threshold] = 255
+        return thresholded
+
+    return nms_img
 
 
 def safe_step(x: np.ndarray, step: int = 2) -> np.ndarray:
diff --git a/tests/app/util/test_controlnet_utils.py b/tests/app/util/test_controlnet_utils.py
index 21662cce8d..9806fe7806 100644
--- a/tests/app/util/test_controlnet_utils.py
+++ b/tests/app/util/test_controlnet_utils.py
@@ -3,6 +3,7 @@ import pytest
 from PIL import Image
 
 from invokeai.app.util.controlnet_utils import prepare_control_image
+from invokeai.backend.image_util.util import nms
 
 
 @pytest.mark.parametrize("num_channels", [1, 2, 3])
@@ -40,3 +41,10 @@ def test_prepare_control_image_num_channels_too_large(num_channels):
             device="cpu",
             do_classifier_free_guidance=False,
         )
+
+
+@pytest.mark.parametrize("threshold,sigma", [(None, 1.0), (1, None)])
+def test_nms_invalid_options(threshold: None | int, sigma: None | float):
+    """Test that an exception is raised in nms(...) if only one of the `threshold` or `sigma` parameters are provided."""
+    with pytest.raises(ValueError):
+        nms(np.zeros((256, 256, 3), dtype=np.uint8), threshold, sigma)