diff --git a/include/cantera/thermo/Phase.h b/include/cantera/thermo/Phase.h
index 745e4f434..6ccc7042e 100644
--- a/include/cantera/thermo/Phase.h
+++ b/include/cantera/thermo/Phase.h
@@ -180,7 +180,9 @@ public:
     //!     @param m  Element index
     doublereal atomicWeight(size_t m) const;
 
-    //! Entropy of the element in its standard state at 298 K and 1 bar
+    //! Entropy of the element in its standard state at 298 K and 1 bar.
+    //! If no entropy value was provided when the phase was constructed,
+    //! returns the value `ENTROPY298_UNKNOWN`.
     //!     @param m  Element index
     doublereal entropyElement298(size_t m) const;
 
diff --git a/src/thermo/Phase.cpp b/src/thermo/Phase.cpp
index d9c9a1a38..2736fb964 100644
--- a/src/thermo/Phase.cpp
+++ b/src/thermo/Phase.cpp
@@ -132,10 +132,7 @@ doublereal Phase::atomicWeight(size_t m) const
 
 doublereal Phase::entropyElement298(size_t m) const
 {
-    AssertThrowMsg(m_entropy298[m] != ENTROPY298_UNKNOWN,
-                   "Elements::entropy298",
-                   "Entropy at 298 K of element is unknown");
-    AssertTrace(m < m_mm);
+    checkElementIndex(m);
     return m_entropy298[m];
 }