diff --git a/src/ILAMB/ConfUncertainty.py b/src/ILAMB/ConfUncertainty.py
index 8a10530..feec4ea 100644
--- a/src/ILAMB/ConfUncertainty.py
+++ b/src/ILAMB/ConfUncertainty.py
@@ -226,7 +226,7 @@ def AnalysisUncertaintySpatial(ref, com, **keywords):
 
     # convert units of the expert value is present
     if expert_uncertainty is not None:
-        match = re.search("(-?\d*\.?\d*)\s(.*)", expert_uncertainty.strip())
+        match = re.search(r"(-?\d*\.?\d*)\s(.*)", expert_uncertainty.strip())
         if match:
             expert_uncertainty = (
                 Variable(data=np.asarray(float(match.group(1))), unit=match.group(2))