diff --git a/src/common/libsys/libsys.c b/src/common/libsys/libsys.c
index 6a834c9..008a3c7 100644
--- a/src/common/libsys/libsys.c
+++ b/src/common/libsys/libsys.c
@@ -46,18 +46,18 @@ void sleep(unsigned ms)
 	usleep(1000*ms);
 }
 
-void usleep(unsigned us)
+void usleep(uint64_t us)
 {
-	unsigned stop_us, stop_s, curr_us, curr_s;
+	uint64_t stop_us, stop_s, curr_us, curr_s;
 	struct timeval t;
 
 	if (!us)
 		return;
 
 	gettimeofday(&t, NULL);
-	stop_s = (unsigned)t.tv_sec;
-	stop_us = (unsigned)t.tv_usec + us;
-	if (stop_us >= 1E6)
+	stop_s = (uint64_t)t.tv_sec;
+	stop_us = (uint64_t)t.tv_usec + us;
+	while (stop_us >= 1E6)
 	{
 		stop_us -= 1E6;
 		stop_s++;
@@ -66,8 +66,8 @@ void usleep(unsigned us)
 	do
 	{
 		gettimeofday(&t, NULL);
-		curr_s = (unsigned)t.tv_sec;
-		curr_us = (unsigned)t.tv_usec;
+		curr_s = (uint64_t)t.tv_sec;
+		curr_us = (uint64_t)t.tv_usec;
 	} while ((curr_s < stop_s) || (curr_us < stop_us));
 
 }
diff --git a/src/common/libsys/libsys.h b/src/common/libsys/libsys.h
index 98195ef..a256fea 100644
--- a/src/common/libsys/libsys.h
+++ b/src/common/libsys/libsys.h
@@ -24,7 +24,7 @@ void print_byte(char byte);
 void print_word(int word);
 void _exit (int exitcode);
 void sleep(unsigned ms);
-void usleep(unsigned us);
+void usleep(uint64_t us);
 
 void PrintBuffer8(uint8_t *pBuf, int nbpr, int len);
 void memdump(uint8_t *pBuf, int print_offset_only, int num_bytes_per_row, int len);