diff --git a/include/openmc/distribution_spatial.h b/include/openmc/distribution_spatial.h
index d66923c4e..ee844aa13 100644
--- a/include/openmc/distribution_spatial.h
+++ b/include/openmc/distribution_spatial.h
@@ -34,9 +34,9 @@ public:
   Position sample(uint64_t* seed) const;
 
   // Observer pointers
-  auto x() const { return x_.get(); }
-  auto y() const { return x_.get(); }
-  auto z() const { return x_.get(); }
+  Distribution* x() const { return x_.get(); }
+  Distribution* y() const { return x_.get(); }
+  Distribution* z() const { return x_.get(); }
 private:
   UPtrDist x_; //!< Distribution of x coordinates
   UPtrDist y_; //!< Distribution of y coordinates