diff --git a/tests/unittests/tests-div/tests-div.c b/tests/unittests/tests-div/tests-div.c
index 699de4874a..30e4e908ed 100644
--- a/tests/unittests/tests-div/tests-div.c
+++ b/tests/unittests/tests-div/tests-div.c
@@ -7,6 +7,7 @@
 */
 
 #include <string.h>
+#include <inttypes.h>
 #include "embUnit.h"
 #include "tests-div.h"
 
@@ -78,7 +79,13 @@ static void test_div_u64_by_15625(void)
     }
 
     for (unsigned i = 0; i < N_U64_VALS; i++) {
+#ifdef PRIu64
         DEBUG("Dividing %12"PRIu64" by 15625...\n", u64_test_values[i]);
+#else
+        DEBUG("Dividing %12"PRIu32"%s by 15625...\n", (uint32_t)u64_test_values[i],
+                ((uint32_t)u64_test_values[i] != u64_test_values[i]) ? "!trunc" : "");
+#endif
+
         TEST_ASSERT_EQUAL_INT(
             (uint64_t)u64_test_values[i] / 15625,
             div_u64_by_15625(u64_test_values[i]));
@@ -105,7 +112,12 @@ static void test_div_u64_by_1000000(void)
     }
 
     for (unsigned i = 0; i < N_U64_VALS; i++) {
+#ifdef PRIu64
         DEBUG("Dividing %"PRIu64" by 1000000...\n", u64_test_values[i]);
+#else
+        DEBUG("Dividing %"PRIu32"%s by 1000000...\n", (uint32_t)u64_test_values[i],
+                ((uint32_t)u64_test_values[i] != u64_test_values[i]) ? "!trunc" : "");
+#endif
         TEST_ASSERT_EQUAL_INT(
             u64_test_values[i] / 1000000lu,
             div_u64_by_1000000(u64_test_values[i]));
@@ -122,7 +134,12 @@ static void test_div_u64_by_15625div512(void)
     }
 
     for (unsigned i = 0; i < N_U64_VALS; i++) {
+#ifdef PRIu64
         DEBUG("Dividing %"PRIu64" by (15625/512)...\n", u64_test_values[i]);
+#else
+        DEBUG("Dividing %"PRIu32"%s by (15625/512)...\n", (uint32_t)u64_test_values[i],
+                ((uint32_t)u64_test_values[i] != u64_test_values[i]) ? "!trunc" : "");
+#endif
         TEST_ASSERT_EQUAL_INT(
             u64_15625_512_expected_values[i],
             div_u64_by_15625div512(u64_test_values[i]));
diff --git a/tests/unittests/tests-frac/tests-frac.c b/tests/unittests/tests-frac/tests-frac.c
index 7236ac61e4..df362b1726 100644
--- a/tests/unittests/tests-frac/tests-frac.c
+++ b/tests/unittests/tests-frac/tests-frac.c
@@ -6,13 +6,12 @@
  * directory for more details.
  */
 
+#include <inttypes.h>
 #include <string.h>
 #include "embUnit.h"
 #include "tests-frac.h"
 
-#include "kernel_defines.h"
 #include "frac.h"
-#include "div.h"
 
 #define ENABLE_DEBUG 0
 #include "debug.h"
@@ -120,11 +119,21 @@ static void test_frac_scale32(void)
                 uint32_t actual = frac_scale(&frac, u32_test_values[i]);
                 if ((uint32_t)expected != actual) {
                     int32_t diff = actual - expected;
+#ifdef PRIu64
                     DEBUG("%" PRIu32 " * (%" PRIu32 " / %" PRIu32 ")"
                         " tmp %" PRIu64 " expect %" PRIu32 ", actual %" PRIu32
                         ", diff = %" PRId32 " shift=%u\n",
                         u32_test_values[i], num, den, tmp, (uint32_t)expected,
                         actual, diff, frac.shift);
+#else
+                    DEBUG("%" PRIu32 " * (%" PRIu32 " / %" PRIu32 ")"
+                        " tmp %" PRIu32"%s expect %" PRIu32 ", actual %" PRIu32
+                        ", diff = %" PRId32 " shift=%u\n",
+                        u32_test_values[i], num, den,
+                        (uint32_t)tmp, ((uint32_t)tmp != tmp) ? "!trunc" : "",
+                        (uint32_t)expected,
+                        actual, diff, frac.shift);
+#endif
 
                     /* The frac algorithm sacrifices accuracy for speed,
                      * some large numbers will be incorrectly rounded,