diff --git a/src/libiso8601/000_TopSource.c b/src/libiso8601/000_TopSource.c
index 4e20f64..087d455 100644
--- a/src/libiso8601/000_TopSource.c
+++ b/src/libiso8601/000_TopSource.c
@@ -13,7 +13,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <inttypes.h>
 #include <sys/time.h>
 
 /* Useful define to alleviate typos */
diff --git a/src/libiso8601/400_manip.c b/src/libiso8601/400_manip.c
index e61f110..f66c131 100644
--- a/src/libiso8601/400_manip.c
+++ b/src/libiso8601/400_manip.c
@@ -100,13 +100,13 @@ void iso8601_subtract_elapsed(struct iso8601_date* date, const struct iso8601_el
 
 void iso8601_add_multiple(struct iso8601_date* date, const struct iso8601_elapsed* per, int n)
 {
-    intmax_t nsec;
-    imaxdiv_t qr;
+    long long nsec;
+    lldiv_t qr;
     struct iso8601_elapsed mult;
 
-    nsec = per->nsec * imaxabs(n);
-    qr = imaxdiv(nsec, BILLION);
-    mult.sec = qr.quot + per->sec * imaxabs(n);
+    nsec = per->nsec * llabs(n);
+    qr = lldiv(nsec, BILLION);
+    mult.sec = qr.quot + per->sec * llabs(n);
     mult.nsec = qr.rem;
 
     if(n < 0) iso8601_subtract_elapsed(date, &mult);
diff --git a/src/libiso8601/build.lib b/src/libiso8601/build.lib
index 7ff8c42..cde6658 100644
--- a/src/libiso8601/build.lib
+++ b/src/libiso8601/build.lib
@@ -12,7 +12,7 @@ then
     source src/libiso8601/soversion
 
     libiso8601="obj/${libiso8601_BASE}.so.${SOMAJOR}.${SOMICRO}"
-    libiso8601_DEP_CFLAGS=""
+    libiso8601_DEP_CFLAGS="-std=gnu99"
     libiso8601_DEP_LIBS="-lrt"
     SO_EXTRA="${libiso8601_DEP_CFLAGS} ${libiso8601_DEP_LIBS} -lc"