diff --git a/njvm.c b/njvm.c
index b7882c0..4bcd8da 100644
--- a/njvm.c
+++ b/njvm.c
@@ -544,7 +544,7 @@ int main(int argc, char *argv[]) {
                 // TODO: implement stack size
             } else if (strcmp(argv[i], "--heap") == 0) {
                 i++;
-                // TODO: implement heap size
+                argVheapSizeKiB = atoi(argv[i]);
             } else if (strcmp(argv[i], "--gcpurge") == 0) {
                 // TODO: implement gcpurge
             } else {