diff -up libsoup-2.62.2/libsoup/soup-xmlrpc.c.coverity-scan-issues libsoup-2.62.2/libsoup/soup-xmlrpc.c
--- libsoup-2.62.2/libsoup/soup-xmlrpc.c.coverity-scan-issues	2018-03-23 14:44:39.000000000 +0100
+++ libsoup-2.62.2/libsoup/soup-xmlrpc.c	2018-06-22 11:40:01.789282049 +0200
@@ -588,7 +588,7 @@ signature_get_next_complete_type (const
 
 			(*signature)++;
 
-			if ( (*signature)[0] == stack[stack_len - 1])
+			if (stack_len > 0 && (*signature)[0] == stack[stack_len - 1])
 				stack_len--;
 		} while (stack_len > 0);
 
