diff --git a/pytools/__init__.py b/pytools/__init__.py
index 97f98f609b57610fc6adc7b97c0627c2a2f79ea5..7e9be32652520fc36590cd5281457922064910ff 100644
--- a/pytools/__init__.py
+++ b/pytools/__init__.py
@@ -1256,8 +1256,16 @@ if __name__ == "__main__":
 
 
 # numpy dtype mangling --------------------------------------------------------
-def common_dtype(dtypes):
-    return argmax2((dtype, dtype.num) for dtype in dtypes)
+def common_dtype(dtypes, default=None):
+    dtypes = list(dtypes)
+    if dtypes:
+        return argmax2((dtype, dtype.num) for dtype in dtypes)
+    else:
+        if default is not None:
+            return default
+        else:
+            raise ValueError(
+                    "cannot find common dtype of empty dtype list")