diff --git a/include/SDL_test_images.h b/include/SDL_test_images.h
index 7917b3abc..ea7222928 100644
--- a/include/SDL_test_images.h
+++ b/include/SDL_test_images.h
@@ -53,7 +53,7 @@ typedef struct SDLTest_SurfaceImage_s {
   int width;
   int height;
   unsigned int bytes_per_pixel; /* 3:RGB, 4:RGBA */ 
-  const unsigned char *pixel_data;
+  const char *pixel_data;
 } SDLTest_SurfaceImage_t;
 
 /* Test images */
diff --git a/test/automated/common/common.h b/test/automated/common/common.h
index d5e7324f5..25e7ecf74 100644
--- a/test/automated/common/common.h
+++ b/test/automated/common/common.h
@@ -22,7 +22,7 @@ typedef struct SurfaceImage_s {
    int width;
    int height;
    unsigned int  bytes_per_pixel; /* 3:RGB, 4:RGBA */ 
-   const unsigned char *pixel_data;
+   const char *pixel_data;
 } SurfaceImage_t;
 
 #define ALLOWABLE_ERROR_OPAQUE	0