diff --git a/rtengine/myfile.cc b/rtengine/myfile.cc
index 11a5b495b..09d9cd48f 100644
--- a/rtengine/myfile.cc
+++ b/rtengine/myfile.cc
@@ -364,7 +364,7 @@ int fscanf (IMFILE* f, const char* s ...)
     char buf[50], *endptr = nullptr;
     int copy_sz = f->size - f->pos;
 
-    if (copy_sz > sizeof(buf)) {
+    if (copy_sz > static_cast<int>(sizeof(buf))) {
         copy_sz = sizeof(buf) - 1;
     }