diff --git a/src/image/format/oslLoadImageFilePNG.c b/src/image/format/oslLoadImageFilePNG.c
index 63789cb..b8bf422 100644
--- a/src/image/format/oslLoadImageFilePNG.c
+++ b/src/image/format/oslLoadImageFilePNG.c
@@ -15,10 +15,10 @@ void oslPngFlushFn(png_structp png_ptr) {
 	// No operation
 }
 
-OSL_IMAGE *oslLoadImageFilePNG(char *filename, int location, int pixelFormat) {
+OSL_IMAGE *oslLoadImageFilePNG(char *filename, int location, int volatile pixelFormat) {
 	const size_t nSigSize = 8;
 	u8 signature[nSigSize];
-	OSL_IMAGE *img = NULL;
+	OSL_IMAGE * volatile img = NULL;
 	VIRTUAL_FILE *f;
 	// We only keep the location bits
 	int imgLocation = location & OSL_LOCATION_MASK;
diff --git a/src/image/format/oslWriteImageFilePNG.c b/src/image/format/oslWriteImageFilePNG.c
index 8329306..4699c31 100644
--- a/src/image/format/oslWriteImageFilePNG.c
+++ b/src/image/format/oslWriteImageFilePNG.c
@@ -15,12 +15,12 @@ void oslPngWriteFn(png_structp png_ptr, png_bytep data, png_size_t length) {
 int oslWriteImageFilePNG(OSL_IMAGE *img, const char* filename, int flags) {
 	png_structp png_ptr = NULL;
 	png_infop info_ptr = NULL;
-	VIRTUAL_FILE *f = NULL;
-	u8* line = NULL;
+	VIRTUAL_FILE * volatile f = NULL;
+	u8* volatile line = NULL;
 	int width = img->offsetX1 - img->offsetX0;
 	int height = img->offsetY1 - img->offsetY0;
 	int r, g, b, a;
-	int lbSuccess = 0;
+	int volatile lbSuccess = 0;
 	const int saveAlpha = flags & OSL_WRI_ALPHA;
 
 	// Open the file for writing
diff --git a/src/sfont.c b/src/sfont.c
index 848b37a..ba68331 100644
--- a/src/sfont.c
+++ b/src/sfont.c
@@ -56,7 +56,7 @@ typedef struct
 // Load a PNG image (OSLib cannot handle images bigger than 512x512)
 static PNG_DATA* _loadFromPNG(const char *filename) {
 	// Allocate memory for PNG_DATA structure
-	PNG_DATA *pngData = (PNG_DATA*)malloc(sizeof(PNG_DATA));
+	PNG_DATA * volatile pngData = (PNG_DATA*)malloc(sizeof(PNG_DATA));
 	if (!pngData)
 		return NULL;
 
@@ -279,7 +279,7 @@ OSL_SFONT *oslLoadSFontFile(char *filename, int pixelFormat) {
 			oslLockImage(lt->letter);
 
 			// Copy the image data into the letter
-			for (int dx = pos; dx < pos + lt->width; ++dx) {
+			for (unsigned int dx = pos; dx < pos + lt->width; ++dx) {
 				for (int dy = 1; dy < img->sizeY; ++dy) {
 					int pixel = _getPixel(img, dx, dy);
 					pixel = oslConvertColorEx(lt->letter->palette, lt->letter->pixelFormat, OSL_PF_8888, pixel);