diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6f284b7..6b57060 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## XAVIER development version
 
+- Fixed syntax warning. (#184, @kelly-sovacool)
+
 ## XAVIER 3.2.2
 
 - Fixed a bug where tumor-only and unpaired runs could fail during Snakefile parsing (#174, @samarth8392)
diff --git a/src/xavier/run.py b/src/xavier/run.py
index eeb823c..8a8c1fe 100644
--- a/src/xavier/run.py
+++ b/src/xavier/run.py
@@ -655,7 +655,7 @@ def get_nends(ifiles):
         nends = {}  # keep count of R1 and R2 for each sample
         for file in ifiles:
             # Split sample name on file extension
-            sample = re.split("\.R[12]\.fastq\.gz", os.path.basename(file))[0]
+            sample = re.split(r"\.R[12]\.fastq\.gz", os.path.basename(file))[0]
             if sample not in nends:
                 nends[sample] = 0