diff --git a/tests/testReading.c b/tests/testReading.c
index d2a2a766171a85ace486914f0f39a987d9d8c3d3..9dda4c7bad75d35a8a93e0c2acb0619409a91afd 100644
--- a/tests/testReading.c
+++ b/tests/testReading.c
@@ -22,7 +22,7 @@
 
 int main() {
 
-  int Ngas = -1, Ngpart = -1;
+  size_t Ngas = 0, Ngpart = 0;
   int periodic = -1;
   int i, j, k, n;
   double dim[3];