diff --git a/dev_requirements.txt b/dev_requirements.txt
index 7a38e1923c..6fb0836d83 100644
--- a/dev_requirements.txt
+++ b/dev_requirements.txt
@@ -30,7 +30,7 @@ nbsphinx==0.9.1
 matplotlib==3.8.1
 pandas==2.1.3
 pyscf==2.5.0; sys_platform != 'win32'
-openfermion==1.6.0; sys_platform != 'win32'
+openfermion==1.6.1; sys_platform != 'win32'
 openfermionpyscf==0.5; sys_platform != 'win32'
 bqskit[ext]==1.0.4
 seaborn==0.13.0
diff --git a/mitiq/rem/inverse_confusion_matrix.py b/mitiq/rem/inverse_confusion_matrix.py
index 2f226ed125..ac52910fd1 100644
--- a/mitiq/rem/inverse_confusion_matrix.py
+++ b/mitiq/rem/inverse_confusion_matrix.py
@@ -36,8 +36,11 @@ def sample_probability_vector(
 
     # split the binary strings into an array of ints
     bitstrings = (
-        np.apply_along_axis(
-            np.fromstring, 1, binary_strings[:, None], dtype="U1"
+        np.apply_along_axis(  # type: ignore
+            func1d=np.fromstring,  # type: ignore
+            axis=1,
+            arr=binary_strings[:, None],
+            dtype="U1",  # type: ignore
         )
         .astype(np.uint8)
         .tolist()