diff --git a/day5/p1.c b/day5/p1.c
index a1112b6..0491fa1 100644
--- a/day5/p1.c
+++ b/day5/p1.c
@@ -5,7 +5,7 @@
 #include <stdint.h>
 
 
-inline int64_t parse_number(const char *end);
+inline uint64_t parse_number(const char *end);
 
 
 int main(int argc, char **argv) {
@@ -69,7 +69,7 @@ int main(int argc, char **argv) {
     return 0;
 }
 
-inline int64_t parse_number(const char *end) {
+inline uint64_t parse_number(const char *end) {
     int64_t num = 0;
 
     for (size_t m = 1;; m *= 10) {
diff --git a/day6/p1.c b/day6/p1.c
index 2559947..9d077b6 100644
--- a/day6/p1.c
+++ b/day6/p1.c
@@ -7,7 +7,7 @@
 
 #define ISDIGIT(c) (c >= 0x30 && c <= 0x39)
 
-inline int64_t parse_number(const char *end);
+inline uint64_t parse_number(const char *end);
 
 
 int main(int argc, char **argv) {
@@ -96,7 +96,7 @@ int main(int argc, char **argv) {
     return 0;
 }
 
-inline int64_t parse_number(const char *end) {
+inline uint64_t parse_number(const char *end) {
     int64_t num = 0;
 
     for (size_t m = 1;; m *= 10) {