diff --git a/tools/fpga_compress/fpga_compress.c b/tools/fpga_compress/fpga_compress.c
index 2174571d6..56dab1865 100644
--- a/tools/fpga_compress/fpga_compress.c
+++ b/tools/fpga_compress/fpga_compress.c
@@ -53,11 +53,13 @@ static void usage(void) {
 
 
 static voidpf fpga_deflate_malloc(voidpf opaque, uInt items, uInt size) {
+    (void) opaque;
     return calloc(items * size, sizeof(uint8_t));
 }
 
 
 static void fpga_deflate_free(voidpf opaque, voidpf address) {
+    (void) opaque;
     free(address);
 }