diff --git a/proto.h b/proto.h
index f993d605..bba7e3f3 100644
--- a/proto.h
+++ b/proto.h
@@ -128,8 +128,8 @@ SR_API char **sr_parse_triggerstring(const struct sr_dev_inst *sdi,
 SR_API int sr_parse_sizestring(const char *sizestring, uint64_t *size);
 SR_API uint64_t sr_parse_timestring(const char *timestring);
 SR_API gboolean sr_parse_boolstring(const char *boolstring);
-SR_API int sr_parse_period(const char *periodstr, struct sr_rational *r);
-SR_API int sr_parse_voltage(const char *voltstr, struct sr_rational *r);
+SR_API int sr_parse_period(const char *periodstr, uint64_t *p, uint64_t *q);
+SR_API int sr_parse_voltage(const char *voltstr, uint64_t *p, uint64_t *q);
 
 /*--- version.c -------------------------------------------------------------*/
 
diff --git a/strutil.c b/strutil.c
index 5b14f51a..f9299ca6 100644
--- a/strutil.c
+++ b/strutil.c
@@ -393,12 +393,12 @@ SR_API gboolean sr_parse_boolstring(const char *boolstr)
 	return FALSE;
 }
 
-SR_API int sr_parse_period(const char *periodstr, struct sr_rational *r)
+SR_API int sr_parse_period(const char *periodstr, uint64_t *p, uint64_t *q)
 {
 	char *s;
 
-	r->p = strtoull(periodstr, &s, 10);
-	if (r->p == 0 && s == periodstr)
+	*p = strtoull(periodstr, &s, 10);
+	if (*p == 0 && s == periodstr)
 		/* No digits found. */
 		return SR_ERR_ARG;
 
@@ -406,17 +406,17 @@ SR_API int sr_parse_period(const char *periodstr, struct sr_rational *r)
 		while (*s == ' ')
 			s++;
 		if (!strcmp(s, "fs"))
-			r->q = 1000000000000000ULL;
+			*q = 1000000000000000ULL;
 		else if (!strcmp(s, "ps"))
-			r->q = 1000000000000ULL;
+			*q = 1000000000000ULL;
 		else if (!strcmp(s, "ns"))
-			r->q = 1000000000ULL;
+			*q = 1000000000ULL;
 		else if (!strcmp(s, "us"))
-			r->q = 1000000;
+			*q = 1000000;
 		else if (!strcmp(s, "ms"))
-			r->q = 1000;
+			*q = 1000;
 		else if (!strcmp(s, "s"))
-			r->q = 1;
+			*q = 1;
 		else
 			/* Must have a time suffix. */
 			return SR_ERR_ARG;
@@ -426,12 +426,12 @@ SR_API int sr_parse_period(const char *periodstr, struct sr_rational *r)
 }
 
 
-SR_API int sr_parse_voltage(const char *voltstr, struct sr_rational *r)
+SR_API int sr_parse_voltage(const char *voltstr, uint64_t *p, uint64_t *q)
 {
 	char *s;
 
-	r->p = strtoull(voltstr, &s, 10);
-	if (r->p == 0 && s == voltstr)
+	*p = strtoull(voltstr, &s, 10);
+	if (*p == 0 && s == voltstr)
 		/* No digits found. */
 		return SR_ERR_ARG;
 
@@ -439,9 +439,9 @@ SR_API int sr_parse_voltage(const char *voltstr, struct sr_rational *r)
 		while (*s == ' ')
 			s++;
 		if (!strcasecmp(s, "mv"))
-			r->q = 1000L;
+			*q = 1000L;
 		else if (!strcasecmp(s, "v"))
-			r->q = 1;
+			*q = 1;
 		else
 			/* Must have a base suffix. */
 			return SR_ERR_ARG;