diff --git a/backend/dmatrix.c b/backend/dmatrix.c
index 5f22b9d0..d4b08039 100644
--- a/backend/dmatrix.c
+++ b/backend/dmatrix.c
@@ -45,7 +45,11 @@
 #include <assert.h>
 #include <math.h>
 #ifdef _MSC_VER
-#include <malloc.h>
+#include <malloc.h>
+/* ceilf (C99) not before MSVC++2013 (C++ 12.0) */
+#if _MSC_VER < 1800
+#define ceilf ceil
+#endif
 #endif
 #include "reedsol.h"
 #include "common.h"
diff --git a/backend/dotcode.c b/backend/dotcode.c
index a3a6c8dd..289e548e 100644
--- a/backend/dotcode.c
+++ b/backend/dotcode.c
@@ -38,10 +38,10 @@
 #include <string.h>
 #include <stdlib.h>
 #include <math.h>
-#include <stdint.h>
 #ifndef _MSC_VER
 #include <stdint.h>
 #else
+#include "ms_stdint.h"
 #include <malloc.h>
 #endif
 #include "common.h"
diff --git a/backend/gif.c b/backend/gif.c
index e9c05834..0883620f 100644
--- a/backend/gif.c
+++ b/backend/gif.c
@@ -272,7 +272,7 @@ int gif_pixel_plot(struct zint_symbol *symbol, char *pixelbuf) {
 #ifndef _MSC_VER
     char lzwoutbuf[symbol->bitmap_height * symbol->bitmap_width];
 #else
-    lzwoutbuf = (char *) _alloca((image_height * image_width) * sizeof (char));
+    lzwoutbuf = (char *) _alloca((symbol->bitmap_height * symbol->bitmap_width) * sizeof (char));
 #endif /* _MSC_VER */
 
     /* Open output file in binary mode */