diff --git a/src/backend/commands/conversioncmds.c b/src/backend/commands/conversioncmds.c
index f067da2..ab744e4 100644
--- a/src/backend/commands/conversioncmds.c
+++ b/src/backend/commands/conversioncmds.c
@@ -49,6 +49,7 @@ CreateConversionCommand(CreateConversionStmt *stmt)
 	const char *to_encoding_name = stmt->to_encoding_name;
 	List	   *func_name = stmt->func_name;
 	static Oid	funcargs[] = {INT4OID, INT4OID, CSTRINGOID, INTERNALOID, INT4OID};
+	char result[1];
 
 	/* Convert list of names to a name and namespace */
 	namespaceId = QualifiedNameGetCreationNamespace(stmt->conversion_name,
@@ -96,6 +97,19 @@ CreateConversionCommand(CreateConversionStmt *stmt)
 					   NameListToString(func_name));
 
 	/*
+	 * Check that the conversion function is suitable for the requested
+	 * source and target encodings. We do that by calling the function with
+	 * an empty string; the conversion function should throw an error if it
+	 * can't perform the requested conversion
+	 */
+	OidFunctionCall5(funcoid, 
+					 Int32GetDatum(from_encoding),
+					 Int32GetDatum(to_encoding),
+					 CStringGetDatum(""),
+					 CStringGetDatum(result),
+					 Int32GetDatum(0));
+
+	/*
 	 * All seem ok, go ahead (possible failure would be a duplicate conversion
 	 * name)
 	 */