diff --git a/platform-independent/c/core/src/mpw-marshal.c b/platform-independent/c/core/src/mpw-marshal.c
index 408f80a2..7acfb9ef 100644
--- a/platform-independent/c/core/src/mpw-marshal.c
+++ b/platform-independent/c/core/src/mpw-marshal.c
@@ -986,6 +986,11 @@ MPMarshalInfo *mpw_marshal_read_info(
         }
     }
 
+    if (info->format == MPMarshalFormatNone) {
+        mpw_marshal_info_free( &info );
+        return NULL;
+    }
+
     return info;
 }
 
diff --git a/platform-independent/c/core/src/mpw-marshal.h b/platform-independent/c/core/src/mpw-marshal.h
index 8c6a088a..42196203 100644
--- a/platform-independent/c/core/src/mpw-marshal.h
+++ b/platform-independent/c/core/src/mpw-marshal.h
@@ -125,8 +125,8 @@ typedef struct MPMarshalInfo {
  * @return A string (allocated), or NULL if the format is unrecognized, does not support marshalling or a format error occurred. */
 const char *mpw_marshal_write(
         const MPMarshalFormat outFormat, const MPMarshalledUser *user, MPMarshalError *error);
-/** Try to read metadata on the sites in the input buffer.
- * @return A metadata object (allocated), or NULL if the object could not be allocated or a format error occurred. */
+/** Best effort parse of metadata on the sites in the input buffer.  Fields that could not be parsed remain at their type's initial value.
+ * @return A metadata object (allocated); NULL if the object could not be allocated or the format was not understood. */
 MPMarshalInfo *mpw_marshal_read_info(
         const char *in);
 /** Unmarshall sites in the given input buffer by parsing it using the given marshalling format.