diff --git a/meson.build b/meson.build
index f6abd9165b8..bde6ec6d5ba 100644
--- a/meson.build
+++ b/meson.build
@@ -1541,7 +1541,8 @@ else
   dep_clock = cc.find_library('rt')
 endif
 
-dep_zlib = dependency('zlib', version : '>= 1.2.9',
+# IMPORTANT: We can't upgrade Zlib beyond 1.2.5 because it would break Viewperf.
+dep_zlib = dependency('zlib', version : '>= 1.2.3',
                       allow_fallback: true,
                       required : get_option('zlib'))
 if dep_zlib.found()
diff --git a/src/util/crc32.c b/src/util/crc32.c
index 59059e4f885..ec5ad2cc94c 100644
--- a/src/util/crc32.c
+++ b/src/util/crc32.c
@@ -33,15 +33,10 @@
  */
 
 
-#include "crc32.h"
 #ifdef HAVE_ZLIB
 #include <zlib.h>
-uint32_t
-util_hash_crc32(const void *data, size_t size)
-{
-   return ~crc32_z(0, data, size);
-}
-#else
+#endif
+#include "crc32.h"
 
 
 static const uint32_t
@@ -122,9 +117,18 @@ util_hash_crc32(const void *data, size_t size)
    const uint8_t *p = data;
    uint32_t crc = 0xffffffff;
 
+#ifdef HAVE_ZLIB
+   /* Prefer zlib's implementation for better performance.
+    * zlib's uInt is always "unsigned int" while size_t can be 64bit.
+    * Since 1.2.9 there's crc32_z that takes size_t, but use the more
+    * available function to avoid build system complications.
+    */
+   if ((uInt)size == size)
+      return ~crc32(0, data, size);
+#endif
+
    while (size--)
       crc = util_crc32_table[(crc ^ *p++) & 0xff] ^ (crc >> 8);
 
    return crc;
 }
-#endif