diff --git a/repos/libports/ports/libc.hash b/repos/libports/ports/libc.hash
index 49ea13a61..f6b196cf1 100644
--- a/repos/libports/ports/libc.hash
+++ b/repos/libports/ports/libc.hash
@@ -1 +1 @@
-15bedbc9f3adea283d1c036ef57448ebbdaa4cbc
+12ac556f17580c447e7502e0485a662610f59c06
diff --git a/repos/libports/run/libc.run b/repos/libports/run/libc.run
index 3a73d49ea..6dd108b37 100644
--- a/repos/libports/run/libc.run
+++ b/repos/libports/run/libc.run
@@ -39,4 +39,4 @@ build_boot_image {
 
 append qemu_args " -nographic  "
 
-run_genode_until "child .* exited with exit value 0.*\n" 13
+run_genode_until "child .* exited with exit value 0.*\n" 30
diff --git a/repos/libports/src/lib/libc/patches/mktime.patch b/repos/libports/src/lib/libc/patches/mktime.patch
new file mode 100644
index 000000000..0860f3e1c
--- /dev/null
+++ b/repos/libports/src/lib/libc/patches/mktime.patch
@@ -0,0 +1,44 @@
+diff --git a/src/lib/libc/contrib/tzcode/stdtime/localtime.c b/src/lib/libc/contrib/tzcode/stdtime/localtime.c
+index 3c66924..05c01ae 100644
+--- src/lib/libc/contrib/tzcode/stdtime/localtime.c
++++ src/lib/libc/contrib/tzcode/stdtime/localtime.c
+@@ -1935,6 +1935,10 @@ time2sub(struct tm *const tmp,
+ 			lo *= 2;
+ 		hi = -(lo + 1);
+ 	}
++
++	lo = TIME_T_MIN;
++	hi = TIME_T_MAX;
++
+ 	for ( ; ; ) {
+ 		t = lo / 2 + hi / 2;
+ 		if (t < lo)
+diff --git a/src/lib/libc/contrib/tzcode/stdtime/private.h b/src/lib/libc/contrib/tzcode/stdtime/private.h
+index 354a78b..8300ba0 100644
+--- src/lib/libc/contrib/tzcode/stdtime/private.h
++++ src/lib/libc/contrib/tzcode/stdtime/private.h
+@@ -251,6 +251,24 @@ const char *	scheck(const char * string, const char * format);
+ 	1 + TYPE_SIGNED(type))
+ #endif /* !defined INT_STRLEN_MAXIMUM */
+ 
++#define TWOS_COMPLEMENT(t) ((t) ~ (t) 0 < 0)
++
++/* Max and min values of the integer type T, of which only the bottom
++   B bits are used, and where the highest-order used bit is considered
++   to be a sign bit if T is signed.  */
++#define MAXVAL(t, b) \
++  ((t) (((t) 1 << ((b) - 1 - TYPE_SIGNED(t))) \
++  - 1 + ((t) 1 << ((b) - 1 - TYPE_SIGNED(t)))))
++#define MINVAL(t, b) \
++  ((t) (TYPE_SIGNED(t) ? - TWOS_COMPLEMENT(t) - MAXVAL(t, b) : 0))
++
++/* The extreme time values, assuming no padding.  */
++#define TIME_T_MIN_NO_PADDING MINVAL(time_t, TYPE_BIT(time_t))
++#define TIME_T_MAX_NO_PADDING MAXVAL(time_t, TYPE_BIT(time_t))
++
++# define TIME_T_MIN TIME_T_MIN_NO_PADDING
++# define TIME_T_MAX TIME_T_MAX_NO_PADDING
++
+ /*
+ ** INITIALIZE(x)
+ */
diff --git a/repos/libports/src/test/libc/main.cc b/repos/libports/src/test/libc/main.cc
index eecbe79a4..8f78792c8 100644
--- a/repos/libports/src/test/libc/main.cc
+++ b/repos/libports/src/test/libc/main.cc
@@ -30,6 +30,9 @@ extern "C" {
 #include <time.h>
 #include <sys/random.h>
 #include <sys/syscall.h>
+#include <sys/limits.h>
+#include <time.h>
+#include <inttypes.h>
 }
 
 int main(int argc, char **argv)
@@ -171,5 +174,34 @@ int main(int argc, char **argv)
 		printf("getentropy %llx\n", buf);
 	}
 
+	do {
+		struct tm tm { };
+		/* 2019-05-27 12:30 */
+		tm.tm_sec  = 0;
+		tm.tm_min  = 30;
+		tm.tm_hour = 12;
+		tm.tm_mday = 27;
+		tm.tm_mon  = 4;
+		tm.tm_year = 119;
+
+		time_t t1 = mktime(&tm);
+		if (t1 == (time_t) -1) {
+			++error_count;
+			long long v1 = t1;
+			printf("Check mktime failed: %lld\n", v1);
+			break;
+		}
+		struct tm *tm_gmt = gmtime(&t1);
+		time_t t2 = mktime(tm_gmt);
+		if (t1 != t2) {
+			++error_count;
+			long long v1 = t1, v2 = t2;
+			printf("Check mktime failed: %lld != %lld\n", v1, v2);
+			break;
+		}
+
+		puts("Check mktime: success");
+	} while (0);
+
 	exit(error_count);
 }