diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index d3482eba9283..86a4beec6528 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -2582,19 +2582,21 @@ int annotate_check_args(void)
 
 int arch__dwarf_regnum(const struct arch *arch, const char *str)
 {
-	const char *p;
+	const char *p = str;
 	char *regname, *q;
 	int reg;
 
-	p = strchr(str, arch->objdump.register_char);
-	if (p == NULL)
-		return -1;
+	if (arch->objdump.register_char) {
+		p = strchr(str, arch->objdump.register_char);
+		if (p == NULL)
+			return -1;
+	}
 
 	regname = strdup(p);
 	if (regname == NULL)
 		return -1;
 
-	q = strpbrk(regname, ",) ");
+	q = strpbrk(regname, ",)] ");
 	if (q)
 		*q = '\0';