--- converter/other/pnmtopng.c
+++ converter/other/pnmtopng.c
@@ -521,7 +521,7 @@
                       unsigned int * const bestMatchP) {
     
     unsigned int paletteIndex;
-    unsigned int bestIndex;
+    unsigned int bestIndex = 0;
     unsigned int bestMatch;
 
     assert(paletteSize > 0);
@@ -2342,7 +2342,7 @@
       /* The color part of the color/alpha palette passed to the PNG
          compressor 
       */
-  unsigned int palette_size;
+  unsigned int palette_size = MAXCOLORS;
 
   gray trans_pnm[MAXCOLORS];
   png_byte  trans[MAXCOLORS];