diff --git a/tests/grib_threads_ecc-604-encode.c b/tests/grib_threads_ecc-604-encode.c
index 3c1bc88c7..992a5c78f 100644
--- a/tests/grib_threads_ecc-604-encode.c
+++ b/tests/grib_threads_ecc-604-encode.c
@@ -117,6 +117,7 @@ int main(int argc, char** argv)
 void* runner(void* ptr)
 {
     do_encode(ptr);
+    free(ptr);
     pthread_exit(0);
 }
 
diff --git a/tests/grib_threads_ecc-604.c b/tests/grib_threads_ecc-604.c
index 7ff78b4b1..8bdcec124 100644
--- a/tests/grib_threads_ecc-604.c
+++ b/tests/grib_threads_ecc-604.c
@@ -169,6 +169,7 @@ int main(int argc, char** argv)
 void* runner(void* ptr)
 {
     do_stuff(ptr);
+    free(ptr);
     pthread_exit(0);
 }