diff --git a/rtengine/iimage.h b/rtengine/iimage.h
index 7e88e407f..b06a188bc 100644
--- a/rtengine/iimage.h
+++ b/rtengine/iimage.h
@@ -1291,7 +1291,7 @@ public:
         b.height_ = height;
 #endif
 
-        abData.resize(width * height * 3);
+        abData.resize(width * height * 3u);
 
         if (!abData.isEmpty()) {
             data = abData.data;
diff --git a/rtengine/image8.cc b/rtengine/image8.cc
index 8cb2b887a..9eaf3afc5 100644
--- a/rtengine/image8.cc
+++ b/rtengine/image8.cc
@@ -67,7 +67,7 @@ void Image8::setScanline (int row, unsigned char* buffer, int bps, float *minVal
 
     switch (sampleFormat) {
     case (IIOSF_UNSIGNED_CHAR):
-        memcpy (data + row * width * 3, buffer, width * 3);
+        memcpy (data + row * width * 3u, buffer, width * 3);
         break;
 
     case (IIOSF_UNSIGNED_SHORT): {