diff --git a/src/debug.c b/src/debug.c
index a9d702b4aa6bf3192ee8b0ccc12a4e556b60295c..03b8fae85bd3e6e9cd3b83067131b1e454b5a775 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -51,7 +51,7 @@
  */
 
 void printParticle(struct part *parts, struct xpart *xparts, long long int id,
-                   int N) {
+                   size_t N) {
 
   int i, found = 0;
 
@@ -66,7 +66,7 @@ void printParticle(struct part *parts, struct xpart *xparts, long long int id,
   if (!found) printf("## Particles[???] id=%lld not found\n", id);
 }
 
-void printgParticle(struct gpart *parts, long long int id, int N) {
+void printgParticle(struct gpart *parts, long long int id, size_t N) {
 
   int i, found = 0;
 
diff --git a/src/debug.h b/src/debug.h
index 3e9fcb6c50603e03ea675176bb0d1a0c02cd12bf..fba5cb68680472715025f9fee39a5bf06abacf81 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -23,9 +23,9 @@
 #include "cell.h"
 #include "part.h"
 
-void printParticle(struct part *parts, struct xpart *xparts, long long int i,
-                   int N);
-void printgParticle(struct gpart *parts, long long int i, int N);
+void printParticle(struct part *parts, struct xpart *xparts, long long int id,
+                   size_t N);
+void printgParticle(struct gpart *parts, long long int id, size_t N);
 void printParticle_single(struct part *p, struct xpart *xp);
 
 #ifdef HAVE_METIS