diff --git a/extras/extras.h b/extras/extras.h
index cc324e9f..6bb7d02a 100644
--- a/extras/extras.h
+++ b/extras/extras.h
@@ -46,7 +46,9 @@ WEBP_EXTERN(int) WebPImportRGB4444(const uint8_t* rgb4444, WebPPicture* pic);
 
 // Parse a bitstream, search for VP8 (lossy) header and report a
 // rough estimation of the quality factor used for compressing the bitstream.
-// Any error (invalid bitstream, lossless compression, incomplete header, etc.)
+// If the bitstream is in lossless format, the special value '101' is returned.
+// Otherwise (lossy bitstream), the returned value is in the range [0..100].
+// Any error (invalid bitstream, animated WebP, incomplete header, etc.)
 // will return a value of -1.
 WEBP_EXTERN(int) VP8EstimateQuality(const uint8_t* const data, size_t size);
 
diff --git a/extras/quality_estimate.c b/extras/quality_estimate.c
index 1466ce92..ee7ab5f8 100644
--- a/extras/quality_estimate.c
+++ b/extras/quality_estimate.c
@@ -12,6 +12,7 @@
 // Author: Skal (pascal.massimino@gmail.com)
 
 #include "./extras.h"
+#include "webp/decode.h"
 
 #include <math.h>
 
@@ -46,9 +47,16 @@ int VP8EstimateQuality(const uint8_t* const data, size_t size) {
   uint64_t sig = 0x00;
   int ok = 0;
   int Q = -1;
+  WebPBitstreamFeatures features;
 
   if (data == NULL) return -1;
 
+  if (WebPGetFeatures(data, size, &features) != VP8_STATUS_OK) {
+    return -1;   // invalid file
+  }
+  if (features.format == 2) return 101;  // lossless
+  if (features.format == 0 || features.has_animation) return -1;   // mixed
+
   while (pos < size) {
     sig = (sig >> 8) | ((uint64_t)data[pos++] << 40);
     if ((sig >> 24) == 0x2a019dull) {
diff --git a/makefile.unix b/makefile.unix
index 5a6d8b14..f1fa8ddb 100644
--- a/makefile.unix
+++ b/makefile.unix
@@ -389,13 +389,13 @@ examples/webpmux: src/mux/libwebpmux.a src/libwebpdecoder.a
 extras/get_disto: extras/get_disto.o
 extras/get_disto: imageio/libimagedec.a
 extras/get_disto: imageio/libimageio_util.a
-extras/get_disto: src/libwebp.a $(EXTRA_LIB)
+extras/get_disto: $(EXTRA_LIB) src/libwebp.a
 extras/get_disto: EXTRA_LIBS += $(CWEBP_LIBS)
 
 extras/webp_quality: extras/webp_quality.o
 extras/webp_quality: imageio/libimagedec.a
 extras/webp_quality: imageio/libimageio_util.a
-extras/webp_quality: src/libwebp.a $(EXTRA_LIB)
+extras/webp_quality: $(EXTRA_LIB) src/libwebp.a
 extras/get_disto: EXTRA_LIBS += $(CWEBP_LIBS)
 
 $(OUT_EXAMPLES) $(EXTRA_EXAMPLES) $(OTHER_EXAMPLES):