diff --git a/sys/include/ztimer/overhead.h b/sys/include/ztimer/overhead.h
index 86637fc32e..521667053c 100644
--- a/sys/include/ztimer/overhead.h
+++ b/sys/include/ztimer/overhead.h
@@ -41,7 +41,7 @@ extern "C" {
  * @param[in]   base    base interval to use
  * @return  (time from ztimer_set() until callback) - base
  */
-uint32_t ztimer_overhead(ztimer_clock_t *clock, uint32_t base);
+int32_t ztimer_overhead(ztimer_clock_t *clock, uint32_t base);
 
 #endif /* ZTIMER_OVERHEAD_H */
 /** @} */
diff --git a/sys/ztimer/overhead.c b/sys/ztimer/overhead.c
index 6502f49cc3..c8d792a0cb 100644
--- a/sys/ztimer/overhead.c
+++ b/sys/ztimer/overhead.c
@@ -35,7 +35,7 @@ static void _callback(void *arg)
     *callback_arg->val = ztimer_now(callback_arg->clock);
 }
 
-uint32_t ztimer_overhead(ztimer_clock_t *clock, uint32_t base)
+int32_t ztimer_overhead(ztimer_clock_t *clock, uint32_t base)
 {
     volatile uint32_t after = 0;
     uint32_t pre;
diff --git a/tests/ztimer_overhead/main.c b/tests/ztimer_overhead/main.c
index 9e2723e2a8..03f258e635 100644
--- a/tests/ztimer_overhead/main.c
+++ b/tests/ztimer_overhead/main.c
@@ -20,6 +20,7 @@
 
 #include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <inttypes.h>
 
 #include "ztimer.h"
@@ -32,16 +33,17 @@ int main(void)
 {
     uint32_t total = 0;
 
-    uint16_t min = 0xFFFF;
-    uint16_t max = 0;
+    int32_t min = INT32_MAX;
+    int32_t max = INT32_MIN;
 
     /* unset configured adjustment */
     /* ZTIMER_USEC->adjust = 0; */
+    printf("ZTIMER_USEC->adjust = %" PRIu32 "\n", ZTIMER_USEC->adjust);
 
     unsigned n = SAMPLES;
     while (n--) {
-        unsigned overhead = ztimer_overhead(ZTIMER_USEC, BASE);
-        total += overhead;
+        int32_t overhead = ztimer_overhead(ZTIMER_USEC, BASE);
+        total += labs(overhead);
         if (overhead < min) {
             min = overhead;
         }
@@ -50,7 +52,8 @@ int main(void)
         }
     }
 
-    printf("min=%u max=%u avg=%" PRIu32 "\n", min, max, (total / SAMPLES));
+    printf("min=%" PRIi32 " max=%" PRIi32 " avg_diff=%" PRIi32 "\n", min, max,
+           (total / SAMPLES));
 
     return 0;
 }
diff --git a/tests/ztimer_overhead/tests/01-run.py b/tests/ztimer_overhead/tests/01-run.py
index 8430a94fea..d838f7a72d 100755
--- a/tests/ztimer_overhead/tests/01-run.py
+++ b/tests/ztimer_overhead/tests/01-run.py
@@ -11,7 +11,7 @@ from testrunner import run
 
 
 def testfunc(child):
-    child.expect(r"min=\d+ max=\d+ avg=\d+\r\n")
+    child.expect(r"min=-?\d+ max=-?\d+ avg_diff=\d+\r\n")
 
 
 if __name__ == "__main__":