diff --git a/wrlib/jpeg.c b/wrlib/jpeg.c
index b1cef8bf..19720572 100644
--- a/wrlib/jpeg.c
+++ b/wrlib/jpeg.c
@@ -133,6 +133,11 @@ RLoadJPEG(RContext *context, char *file_name, int index)
   
     jpeg_read_header(&cinfo, TRUE);
 
+    if (cinfo.image_width < 1 || cinfo.image_height < 1) {
+	RErrorCode = RERR_BADIMAGEFILE;
+	goto bye;
+    }
+
     bptr = buffer[0] = (JSAMPROW)malloc(cinfo.image_width*cinfo.num_components);
     if (!buffer[0]) {
 	RErrorCode = RERR_NOMEMORY;
diff --git a/wrlib/nxpm.c b/wrlib/nxpm.c
index 8fcfc10a..aa1dcb63 100644
--- a/wrlib/nxpm.c
+++ b/wrlib/nxpm.c
@@ -86,7 +86,7 @@ RGetImageFromXPMData(RContext *context, char **data)
     int w, h, ccount, csize;
 
     if (sscanf(data[line++], "%i %i %i %i", &w, &h, &ccount, &csize)!=4
-	|| w <= 0 || h <= 0 || ccount <= 0 || csize <= 0)
+	|| w <= 1 || h <= 1 || ccount <= 0 || csize <= 0)
 	goto bad_format;
     
     if (csize!=1 && csize!=2) 
diff --git a/wrlib/png.c b/wrlib/png.c
index e814ee35..28349d02 100644
--- a/wrlib/png.c
+++ b/wrlib/png.c
@@ -112,6 +112,15 @@ RLoadPNG(RContext *context, char *file, int index)
     png_get_IHDR(png, pinfo, &width, &height, &depth, &color_type,
 		 &junk, &junk, &junk);
 
+
+    /* sanity check */
+    if (width < 1 || height < 1) {
+	fclose(f);
+	png_destroy_read_struct(&png, &pinfo, &einfo);
+	RErrorCode = RERR_BADIMAGEFILE;
+	return NULL;
+    }
+
     
     /* check for an alpha channel */
     if (png_get_valid(png, pinfo, PNG_INFO_tRNS))
diff --git a/wrlib/ppm.c b/wrlib/ppm.c
index 1e2a381e..65749292 100644
--- a/wrlib/ppm.c
+++ b/wrlib/ppm.c
@@ -154,7 +154,7 @@ RLoadPPM(RContext *context, char *file_name, int index)
     }
     
     /* get size */
-    if (sscanf(buffer, "%i %i", &w, &h)!=2)
+    if (sscanf(buffer, "%i %i", &w, &h)!=2 || w < 1 || h < 1)
 	goto bad_file;